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Final le arthrology guide table 25

Lower Extremity Arthrology Guide

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Final le arthrology guide table 25

  1. 1.     1   Arthrology  Guide   of  the  Lower  Extremity   Kylie  Bauman,  Jessie  Brown,  Sivan  Fogel,  Mariah  Granzella,   Michael  Kaspin,  Kelsey  Poos-­‐Benson,  Megan  Smith,  Allie  Stone  
  2. 2. Lower Extremity Arthrology   2   Table of Contents Hip Joint Complex  _________________________________________________________________________________________  6   Introduction  _____________________________________________________________________________________________________  6   Muscles  of  the  Hip  Joint  Complex  ______________________________________________________________________________  6   Symphysis Pubis Joint  ____________________________________________________________________________________________  8   Overview  ________________________________________________________________________________________________________  8   Tissue  Layers   ___________________________________________________________________________________________________  8   Joint  Motion  _____________________________________________________________________________________________________  9   Biomechanics  ___________________________________________________________________________________________________  9   Joint  Configuration  ____________________________________________________________________________________________  10   Ligaments  of  the  Symphysis  Pubis  ___________________________________________________________________________  10   Common  Joint  Pathology  ______________________________________________________________________________________  11   Sacroiliac Joint  ___________________________________________________________________________________________________  11   Overview  _______________________________________________________________________________________________________  11   Tissue  Layers   __________________________________________________________________________________________________  13   Joint  Motions  ___________________________________________________________________________________________________  13   Biomechanics  __________________________________________________________________________________________________  13   Joint  Configuration  ____________________________________________________________________________________________  17   Ligaments  of  the  Sacroiliac  ___________________________________________________________________________________  18   Common  Joint  Pathology  ______________________________________________________________________________________  18   Femoroacetabular Joint  _________________________________________________________________________________________  19   Overview  _______________________________________________________________________________________________________  19   Tissue  Layers   __________________________________________________________________________________________________  20   Joint  Motions  ___________________________________________________________________________________________________  21   Biomechanics  __________________________________________________________________________________________________  21   Joint  Configuration  ____________________________________________________________________________________________  25   Ligaments  of  the  Femoral  Acetabular  ________________________________________________________________________  27   Common  Joint  Pathology  ______________________________________________________________________________________  28   Knee Joint Complex  ______________________________________________________________________________________  30   Introduction  ____________________________________________________________________________________________________  30   Muscles  of  the  Knee  Joint  Complex  ___________________________________________________________________________  31   Tibiofemoral Joint  _______________________________________________________________________________________________  32   Overview  _______________________________________________________________________________________________________  32   Tissue  Layers   __________________________________________________________________________________________________  32   Joint  Motions  ___________________________________________________________________________________________________  34   Biomechanics  and  Joint  Configuration  _______________________________________________________________________  34   Ligaments  of  the  Tibiofemoral  ________________________________________________________________________________  37   Common  Joint  Pathology  ______________________________________________________________________________________  38   Patellofemoral Joint  ______________________________________________________________________________________________  40   Overview  _______________________________________________________________________________________________________  40   Tissue  Layers   __________________________________________________________________________________________________  41   Joint  Motion  ____________________________________________________________________________________________________  42   Biomechanics  __________________________________________________________________________________________________  42   Ligaments  of  the  Patellofemoral  Joint  ________________________________________________________________________  45   Common  Joint  Pathology  ______________________________________________________________________________________  45  
  3. 3. Lower Extremity Arthrology Guide 3   Foot and Ankle Joint Complex  __________________________________________________________________________  48   Overview  _______________________________________________________________________________________________________  48   Muscles  of  the  Ankle  Joint  Complex  __________________________________________________________________________  49   Muscles  of  the  Foot  Joint  Complex  ___________________________________________________________________________  50   Proximal Tibiofibular Joint  _____________________________________________________________________________________  51   Overview  _______________________________________________________________________________________________________  51   Tissue  Layers   __________________________________________________________________________________________________  52   Joint  Motion  ____________________________________________________________________________________________________  53   Biomechanics  __________________________________________________________________________________________________  53   Joint  Configuration  ____________________________________________________________________________________________  54   Ligaments  of  the  Proximal  Tibiofibular  ______________________________________________________________________  55   Common  Pathology  ____________________________________________________________________________________________  55   Distal Tibiofibular joint  _________________________________________________________________________________________  56   Overview  _______________________________________________________________________________________________________  56   Tissue  Layers   __________________________________________________________________________________________________  56   Joint  Motions  ___________________________________________________________________________________________________  57   Biomechanics  and  Joint  Configuration  _______________________________________________________________________  57   Ligaments  of  the  Distal  Tibiofibular  __________________________________________________________________________  58   Common  Joint  Pathology  ______________________________________________________________________________________  58   The Talocrural Joint  _____________________________________________________________________________________________  59   Overview  _______________________________________________________________________________________________________  59   Tissue  Layers   __________________________________________________________________________________________________  59   Joint  Motions  ___________________________________________________________________________________________________  60   Biomechanics  and  Joint  Configuration  _______________________________________________________________________  60   Ligaments  of  the  Talocrural   __________________________________________________________________________________  62   Common  Joint  Pathology  ______________________________________________________________________________________  62   Subtalar Joint  ____________________________________________________________________________________________________  63   Overview  _______________________________________________________________________________________________________  63   Tissue  Layers   __________________________________________________________________________________________________  64   Joint  Motions  ___________________________________________________________________________________________________  65   Biomechanics  __________________________________________________________________________________________________  65   Joint  Configuration  ____________________________________________________________________________________________  66   Ligaments  of  the  Subtalar  _____________________________________________________________________________________  67   Common  Joint  Pathology  ______________________________________________________________________________________  67   Transverse Tarsal Joint (Calcaneocuboid Joint and Talonavicular joint)  __________________________________  69   Overview  _______________________________________________________________________________________________________  69   Tissue  Layers   __________________________________________________________________________________________________  69   Joint  Motions  ___________________________________________________________________________________________________  70   Biomechanics  __________________________________________________________________________________________________  70   Joint  Configuration  ____________________________________________________________________________________________  72   Ligaments  of  the  Transverse  tarsal  joint  (Calcaneocuboid  Joint  and  Talonavicular  joint)  ______________  73   Common  Joint  Pathology  ______________________________________________________________________________________  73   Cuneonavicular joint (Distal intertarsal joint)  ________________________________________________________________  74   Overview  _______________________________________________________________________________________________________  74   Tissue  Layers   __________________________________________________________________________________________________  74   Joint  Motions  ___________________________________________________________________________________________________  75  
  4. 4. Lower Extremity Arthrology   4   Biomechanics  __________________________________________________________________________________________________  75   Joint  Configuration  ____________________________________________________________________________________________  76   Ligaments  of  the  Cuneonavicular  or  Distal  Intertarsal  _____________________________________________________  77   Common  Pathology  ____________________________________________________________________________________________  77   Cuboideonavicular Joint  ________________________________________________________________________________________  78   Overview  _______________________________________________________________________________________________________  78   Tissue  Layers   __________________________________________________________________________________________________  78   Joint  Motions  ___________________________________________________________________________________________________  79   Biomechanics  __________________________________________________________________________________________________  79   Joint  Configuration  ____________________________________________________________________________________________  80   Ligaments  of  the  Cuboideonavicular  _________________________________________________________________________  80   Common  Joint  Pathology  ______________________________________________________________________________________  80   Intercuneiform and Cuneocuboid Joints  _______________________________________________________________________  80   Overview  _______________________________________________________________________________________________________  80   Tissue  Layers   __________________________________________________________________________________________________  81   Joint  Motions  ___________________________________________________________________________________________________  82   Biomechanics  __________________________________________________________________________________________________  82   Joint  Configuration  ____________________________________________________________________________________________  82   Ligaments  of  the  Intercuneiform  and  Cuneocuboid  ________________________________________________________  83   Common  Joint  Pathology  ______________________________________________________________________________________  83   Tarsometatarsal Joints  __________________________________________________________________________________________  84   Overview  _______________________________________________________________________________________________________  84   Tissue  Layers   __________________________________________________________________________________________________  85   Joint  Motions  ___________________________________________________________________________________________________  86   Biomechanics  __________________________________________________________________________________________________  86   Joint  Configuration  ____________________________________________________________________________________________  88   Ligaments  of  the  Tarsometatarsals  __________________________________________________________________________  89   Common  Joint  Pathology  ______________________________________________________________________________________  90   Intermetatarsal Joints  ___________________________________________________________________________________________  90   Overview  _______________________________________________________________________________________________________  90   Tissue  Layers   __________________________________________________________________________________________________  91   Joint  Motions  ___________________________________________________________________________________________________  92   Biomechanics  __________________________________________________________________________________________________  92   Joint  Configuration  ____________________________________________________________________________________________  93   Ligaments  of  the  Intermetatarsal  Joints  _____________________________________________________________________  93   Common  Joint  Pathology  ______________________________________________________________________________________  93   Metatarsophalangeal Joint (MTP joints)  ______________________________________________________________________  95   Overview  _______________________________________________________________________________________________________  95   Tissue  Layers   __________________________________________________________________________________________________  95   Joint  Motions  ___________________________________________________________________________________________________  96   Biomechanics  __________________________________________________________________________________________________  96   Joint  Configuration  ____________________________________________________________________________________________  97   Ligaments  of  the  Metatarsophalangeal  ______________________________________________________________________  98   Common  Joint  Pathology  ______________________________________________________________________________________  98   Interphalangeal Joints  ___________________________________________________________________________________________  99   Overview  _______________________________________________________________________________________________________  99  
  5. 5. Lower Extremity Arthrology Guide 5   Tissue  Layers   __________________________________________________________________________________________________  99   Joint  Motions  _________________________________________________________________________________________________  100   Biomechanics  ________________________________________________________________________________________________  100   Joint  Configuration  __________________________________________________________________________________________  101   Ligaments  of  the  Interphalangeals  _________________________________________________________________________  101   Common  Pathology  __________________________________________________________________________________________  101        
  6. 6. Lower Extremity Arthrology   6   Hip Joint Complex Introduction   The hip joint complex is the critical link between the lower extremity and the trunk. This system must absorb and transmit enormous forces while also allowing a large arc of motion. The hip joint complex is made up of four joints: the femoroacetabular joint, the right and left sacroiliac (SI) joints, and the pubic symphysis. Typically, the femoroacetabular joint is referred to as the hip joint. This is the ball and socket articulation where most of our lower extremity range of motion comes from. However; the SI joints and the pubic symphysis create the stable ring of the pelvis and may affect how the hip can function in open and closed kinetic chain. The pelvis is made up of two innominates created by the ileum, ischium and pubis, which are connected anteriorly at the symphysis pubis and posterior at the right and left sacroiliac (SI) joints. The innominate bones fuse together forming the acetabulum where the head of the femur articulates wit the pelvis. The SI joint is an articulation between the sacrum of the spinal column and the ileum bones of the pelvis. The pubic symphysis is the articulation between the two pubic bones of the pelvis. The common hip joint complex has three distinct functions, it acts as attachment site for various muscles and connective tissues, supports the organs such as the urinary bladder and intestines, and helps transmit weight from the appendicular to axial skeleton. Muscles of the Hip Joint Complex Category Muscle Function Origin Insertion Nerve Blood Supply Gluteal Region Gluteus maximus Hip extensor External rotator (H) Surface of ilium, sacrum and coccyx Iliotibial tract and gluteal tuberosity of the femur Inferior gluteal (L5, S1, S2) Inf. & Sup. Gluteal Gluteus medius Hip abductor Internal rotator (H) Surface of ilium Greater trochanter Superior gluteal Superior gluteal Gluteus minimus Hip abductor Internal rotator (H) Surface of ilium Greater trochanter Superior gluteal Superior gluteal Tensor Fascia Latae Med rotation, flexion of the hip. Abduction Outer surface of ilium Iliotibial tract Superior gluteal Superior gluteal Pelvic Region Gluteus maximus Hip extensor External rotator (H) Surface of ilium, sacrum and coccyx Iliotibial tract and gluteal tuberosity of femur Inferior gluteal Inf. & Sup. Gluteal Piriformis External rotator (H) Sacrum Greater trochanter Sacral plexus Inf. & Sup. Gluteal Superior gemellus External rotator (H) Ischial spine Greater trochanter Sacral plexus Inf. Gluteal
  7. 7. Lower Extremity Arthrology Guide 7   Inferior gemellus External rotator (H) Ischial tuberosity Greater trochanter Sacral plexus Inf. Gluteal Obturator internus External rotator (H) Inner surface of obturator foramen Greater trochanter Sacral plexus Inf. Gluteal Obturator externus External rotator (H) Outer surface of obturator foramen Greater trochanter Obturator Med. circumflex femoral & Obturator Anterior Thigh Pectineus Hip Flexor Hip Adductor Pubic ramus Upper medial femur Femoral Med. Circumflex femoral & Obturator Sartorius Hip Flexor Hip Abductor External rotator (H) Knee extensor Anterior superior iliac spine Upper medial tibia Femoral Femoral Rectus femoris Hip Flexor Hip Extensor External rotator (H) Upper shaft of femur Patellar ligament Femoral Lateral circumflex femoral Vastus medialis Hip Extensor External rotator (H) Upper shaft of femur Patellar ligament Femoral Femoral Vastus lateralis Hip Extensor External rotator (H) Upper shaft of femur Patellar ligament Femoral Lateral circumflex femoral Vastus intermedius Hip Extensor External rotator (H) Upper shaft of femur Patellar ligament Femoral Lateral circumflex femoral Category Muscle Function Origin Insertion Nerve Blood Supply Medial Thigh Gracilis Knee Flexor Hip Adductor Pubic ramus Upper medial tibia Obturator Med circumflex femoral & obturator Adductor magnus Hip Adductor External rotator (H) Pubic ramus Posterior surface of shaft of femur Obturator Med circumflex femoral & obturator Adductor brevis Hip Adductor External rotator (H) Pubic ramus Posterior surface of shaft of femur Obturator Med circumflex femoral & obturator Adductor Longus Hip Adductor External rotator (H) Pubic ramus Posterior surface of shaft of femur Obturator Med circumflex femoral & obturator Posterior Thigh Semitendinosus Hip Extensor Knee Flexor Ischial tuberosity Medial condyle of tibia Tibial Perforating br. Of deep femoral Semimembranosus Hip Extensor Knee Flexor Ischial tuberosity Medial condyle of tibia Tibial Perforating br. Of deep femoral Long head of biceps femoris Hip Extensor Knee Flexor External rotator (H) Ischial tuberosity Fibular head Tibial Perforating br. Of deep femoral Short head of biceps femoris Knee Flexor External rotator (H) Lateral shaft of femur Fibular head Fibular Perforating br. Of deep femoral Hamstring part of adductor magnus Hip Extensor Ischial Tuberosity Medial shaft of femur (adductor tubercle) Tibial Perforating br. Of deep femoral
  8. 8. Lower Extremity Arthrology   8   Symphysis Pubis Joint Overview The symphysis pubis joint primarily acts as a stabilizer to allow some mobility in the pelvic ring without compromising stability of the lower extremity and trunk. It is a synarthrosis fibrocartilaginous joint, joined together by a fibrocartilaginous disc; called the interpubic disc. The interpubic disc is situated between two layers of hyaline cartilage that line the medial articular surfaces of the two pubic bones. The joint is further reinforced by a series of ligaments and tendinous sheaths that stabilize the symphysis pubis and prevent excessive separation, compression, shift, or rotation from occurring. The symphysis pubis helps to disperse force transmitted from the lower extremity up through the pelvic ring to the axial skeleton during gait and impact activity. It is not commonly injured, but joint laxity during pregnancy and postpartum can result in pelvic dysfunction and symphysis pubis pain. As it is not a synovial joint, no joint capsule exists and instead the joint articulates via the interpubic disc. This joint does not act in physiological kinematics and arthrokinematics beyond a few degrees of shift or rotation are indicative of dysfunction and may lead to pain. Even so, the symphysis pubis is key to allowing pelvic ring pliability during childbirth while maintaining a stable structure for large force distribution in everyday activity. Tissue Layers • Skin o Epidermis o Dermis o Hypodermis • Subcutaneous tissue o Camper’s Fascia o Scarpa’s Fascia • Rectus Abdominis Sheath o External Oblique mm. and aponeurosis o Internal Oblique mm. and aponeurosis o Transversus Abdominis mm. and aponeurosis o Rectus abdominis mm. o Transversalis Fascia Figure  1  Interpubic  disc
  9. 9. Lower Extremity Arthrology Guide 9   • Tendons o Adductor Brevis o Adductor Longus o Pectineus o Gracilis o Adductor magnus o Quadratus o Obturator externus • Neurovasculature o Obturator aa. and vv. o Inferior epigastric aa. and vv. o Pudendal nn. o Genital branch of genitofemoral nn. o Iliohypogastric/ilioinguinal nn. • Ligaments o Superior pubic ligament o Anterior pubic ligament o Inferior pubic (arcuate) ligament o Posterior pubic ligament o Inguinal Ligament • Bones o Pubic Bones • Interpubic disc Joint Motion Joint Motion* Primary Movers Secondary Movers 2mm Shift (inferior/superior) Gravity, ground reaction force through LE Adductor brevis, longus, gracilis, rectus abdominis, external oblique aponeurosis N/A 1° Rotation Same* N/A *Due to the stability of the pubic symphysis, no muscles act directly on it. Rather, gravity and ground reaction forces indirectly shift and rotate its approximation as well as conjunct movement of muscles that attach here. Biomechanics The two pubic bones have medial hyaline cartilage-covered articulating surfaces. They articulate at midline as reinforced by many ligaments and fibrocartilage connections. The articulating surfaces contain small ridges to increase stability and resist shear forces. The interpubic disc lies in between the joint surfaces providing a binding surface. The joint is primarily subject to compression forces at its superior border and tensile forces at its inferior border with everyday activity of sitting and walking; especially during single limb stance due to activity of the rectus sheath superiorly and the Figure  2  Muscular  reinforcement  of  pubic  symphysis
  10. 10. Lower Extremity Arthrology   10   adductor tendons inferiorly as Figure 2 illustrates. The joint allows up to 2mm of translation in the sagittal plane and 1° of rotation. The average displacement of the pubic bones in any direction (most prominently during single limb stance) is 1-2mm higher in women who have bore children compared to both men and nulliparous women. The joint is strongly reinforced via four ligamentous structures. According to Ibrahim & El-Sherbini in 1961, the ligaments from strongest to weakest were anterior: inferior: superior; with no data provided on the posterior pubic ligament. The strength of these ligaments were strongest in men, then nulliparous women, then women who had children, and weakest in women during their third trimester of pregnancy. Joint Configuration According to Becker et al. the most current anatomical and arthrodial evidence reported on the symphysis pubis is from 1990. In Becker et al.’s 2010 systematic review, they concluded that the articular surfaces of the pubic bones are slightly convex, oval shaped and running posteroinferiorly in a craniocaudal direction. Posteriorly the surfaces are parallel but separate anterior and superiorly. The subchondral bone begins rough and uneven in childhood, but is relatively smooth by 30 years of age. As degenerative changes occur in late adulthood, the subchondral bone surface roughens again by age 60. Ligaments of the Symphysis Pubis Ligament Attachments Function Other constraints Superior Pubic Ligament Bilateral pubic crests as far laterally as pubic tubercles, interpubic disc, pectineal ligament, linea alba Controversial but most likely reinforcement of superior portion of joint Stability Inferior Pubic Ligament (subpubic, arcuate) Inferior pubic rami bilaterally, interpubic disc Reinforce inferior portion of joint Stability Anterior Pubic Ligament Anterior pereosteum of pubic bones bilaterally. Interpubic disc Reinforce anterior symphysis pubis Strongest ligament of symphysis pubis. Posterior pubic ligament A few thin fibers spanning posterior symphysis pubis, blending with pubic rami pereosteum and superior and inferior pubic ligaments. Reinforce symphysis pubis joint Stability Interpubic Disc (fibrocartilaginous) Medial articular surfaces of bilateral pubic bones, fused with superior, inferior, anterior, posterior pubic ligaments Withstand compressive and tensile stresses Stability, maintain pelvic ring integrity Figure  3  Bony  features  of  symphysis  pubis
  11. 11. Lower Extremity Arthrology Guide 11   Common Joint Pathology Parturition-Induced Pelvic Instability. The symphysis pubis is relatively immobile and so most pathologies related to its anatomy are due to excessive mobility. The most common pathology of the symphysis itself is parturition-induced pelvic instability. This is excessive mobility and pain of the symphysis pubis due to increases in relaxin and progesterone hormones during and after childbirth in women. The symphysis can widen in women after childbirth 3-7mm and is treated conservatively with a brace to promote compression of the symphysis, muscular strengthening to increase dynamic stability and modified activity. Pelvic Fracture. In addition to childbirth, acute trauma can cause mass instability of the symphysis pubis. An open book pelvic fracture is a fracture to the pelvic ring induced from an anterior to posterior compression force. This causes the symphysis pubis to separate and open the pelvis up like a book. This fracture is often accompanied by sacroiliac joint pain and pathology. This is a devastating injury necessitating surgery to repair arteries and manage blood loss as well as reapproximate the symphysis pubis. Osteitis Pubis. An additional common pathology of the symphysis pubis is osteitis pubis. This is inflammation of the symphysis pubis due to a variety of irritants. The most common causes of osteitis pubis are high level of athletic activity disrupting adductor tendon attachments to the pubis, childbirth disruption of the joint, or secondary effects of urologic or gynecologic surgery. Sacroiliac Joint Overview Sacroiliac (SI) joint is the articulation between the ilium and the sacrum. This joint is designed for stability and transfer of either light loads or heavy loads. These loads are transferred through vertebral column, lower extremities, and the ground. The SI joint is made up of the articulation of the sacrum with the ilium on each side. The articular surfaces are ear shaped, containing irregular ridges and depressions. The concave sacral surface is Figure  4  Sacroiliac  bony  structure
  12. 12. Lower Extremity Arthrology   12   covered with thick hyaline cartilage and the convex iliac surface is lined with thin fibrocartilage. The joint is comprised of strong and dense ligamentous structures that contribute to the SI joint being one of the most stable joints in the body. Numerous muscles also attach to the SI joint that assist in stabilizing the joint. The SI joint configuration undergoes changes during aging that are related to dysfunction. In adolescence the SI joint is mostly synovial with smooth articular surfaces. This smooth surface of the joint in early childhood permits gliding motions in all directions. Through puberty and entering adulthood, the joint characteristics change. The joint becomes part syndesmosis and part synovial. The articular surfaces also change from smooth to more rough and irregular between puberty and adulthood. The irregular and rough surface changes happen on both the articular surfaces and the subchondral bone. The joint also becomes less mobile through the aging process. The ligaments that cover the joint become more fibrotic and less elastic. The hyaline cartilage that covers the concave sacral surface thins and may cause adhesions to occur between the sacrum and the ilium. Due to these changes, motion (primarily rotation) becomes minimal and the joint becomes more mature and stable. Anatomical features of the joint also differ with gender. The female sacrum is shorter, wider, and more posteriorly curved than the male sacrum to provide more room for the passage of the newborn through the birth canal during childbirth. The male sacrum is long, narrow, straighter, and has a more pronounced sacral promontory. These differences are due to greater imposed forces on the joint in males compared to females according to Vleeming et al. The sacroiliac ligaments in women are more elastic than men’s, allowing the mobility necessary for childbirth. Neurovasculature. Blood supply to the joint is derived from iliolumbar, superior gluteal, and lateral sacral arteries. The sacroiliac joint is also well innervated. According to Forst SL; histological analysis of the sacroiliac joint has verified the presence of nerve fibers within the joint capsule and adjoining ligaments. It has been variously described that the sacroiliac joint receives its innervations from the ventral rami of L4 and L5, the superior gluteal nerve, and the dorsal rami of L5, S1, and S2.
  13. 13. Lower Extremity Arthrology Guide 13   Tissue Layers • Integumentary o Epidermis o Dermis o Hypodermis • Superficial fascia o Subcutaneous tissue o Stored fat o Loose connective tissue o Neurovasculature • Muscles/Fascia o Thoracolumbar fascia § Posterior layer § Lateral raphe § Middle layer § Anterior Layer o Erector Spinae § Iliocostalis § Longissimus o Gluteus maximus o Gluteus medius o Gluteus minimus o Piriformis o Iliacus o Psoas Major • Ligaments • Joint articular surfaces Joint Motions Joint Motion* Associated Muscles Stability Biceps femoris, Gluteus maximus, Latissimus dorsi, Iliacus, Piriformis Erector spinae, Lumbar multifidi, Rectus abdominis, Internal abdominal obliques, Transversus abdominis Nutation Biceps femoris, Erector spinae, Rectus abdominis Counternutation Rectus femoris, Tensor fascia latae, Adductor longus, Pectineus * It should be noted that movement at the SI joint occurs secondarily due to movement of the innominate bones. No muscle directly acts on the SI joint. Biomechanics The articular surface of the ilium is convex and the articular surface of the sacrum is slightly concave. The SI joint permits a small amount of motion that varies among individuals. The smooth SI joint surfaces in early childhood permit gliding motions in all directions, which is typical of a synovial plane joint. However, after puberty, the joint surfaces change their configuration and motion in the adult is restricted to a few millimeters. Due to the congruency of the joint, movement is described as the concave sacrum moving on the convex ilium.
  14. 14. Lower Extremity Arthrology   14   When the movement does occur at the ilium, the movement that describes the movement at the sacrum is described as nutation and counternutation. These motions occur around its mediolateral axis at the level of S2 and are limited to the near sagittal plane. Nutation occurs as the sacrum moves anteriorly and inferiorly while the coccyx moves posteriorly relative to the ilium. Nutation occurs with a posterior iliac tilt. Counternutation is simply the opposite and occurs when the sacrum moves posteriorly and superiorly while the coccyx moves anteriorly relative to the ilium. Counternutation occurs with anterior pelvic tilt. Ilium-on-sacral rotation, sacral-on ilium rotation, or complimentary motion of both can accomplish nutation and counternutation. These motions help transfer the forces between the axial skeleton and lower extremities. During gait, the SI joint is very important as it is the location for force transmission from the trunk to the ground and from the ground to the trunk. In order for the forces to be transferred efficiently the joint has to be stable. Stability of the joint comes from strong, fibrous ligaments, the irregular articular surfaces of the ilium and sacrum, and muscular stabilizers. Stability of the SIJs is extremely important because these joints must support a large portion of the body weight. In normal erect posture, the weight of head, arms, and trunk (HAT) is transmitted through the fifth lumbar vertebra and lumbosacral disk to the first sacral segment. The joint must support significantly more than the weight of the body if an individual is lifting or carrying weighted objects As noted earlier the SI joint is very stable joint with minimal movement. The movement that does occur at the joint is very important for stress relief during walking, running, and during childbirth in women. During walking, the pelvis rotates from side to side as the lower extremity changes from a position of flexion to extension. In normal gait with typical speed, the heel of advancing lower limb strikes the ground as the toes of the opposite limb are still in contact with the support. It is this point in gait that the ligaments and muscles at the hips create oppositely directed torsions on the right and left iliac crests. Torsions are most notable in sagittal and Figure  5  Nutation  and  Counternutation  of  SI  joint
  15. 15. Lower Extremity Arthrology Guide 15   horizontal plane. If the SI joint was a solid and continues structure, the SI joint would not be able to dissipate damaging stress and the pelvic ring would be damaged with everyday activity. Gravity is the first line of stability for the SI joint. In an upright position the bodies center of mass is just anterior to S2, which is the midpoint between an imaginary line connecting the two SI joints The downward force of gravity that is a result from the body weight passing through the vertebra forces the trunk downwards on the sacrum while the joint transfers weight from the lower extremity to the spine. This creates a nutation moment about the joint. At the same time, ground reaction forces act on the femoral head, causing an upward directed compression force through the acetabulum. This forces the ilium to rotate posteriorly. The nutation moment created by gravity and the ground reaction force causing the ilium to rotate posteriorly creates a locking mechanism. This locking mechanism relies primarily on gravity and congruity of the joint surfaces rather than the extra-articular structures such as ligaments and muscles. Ligaments also provide stability to the joint as the ligaments of the sacrum are some of the strongest and toughest ligaments in the body that are difficult to tear, stretch, and mobilize. The primary stabilizing ligaments of the SI joint are the interosseous sacroiliac, anterior sacroiliac, iliolumbar, and posterior sacroiliac ligaments as illustrated in Figure 6 and 7. The secondary ligaments that stabilize the sacrum are the sacrotuberous and sacrospinous ligaments. The interosseous sacroiliac ligament strongly and rigidly binds the sacrum with the ilium. The major function of the interosseous sacroiliac ligament is to prevent abduction or distraction of the sacroiliac joint. It is also the interosseous sacroiliac ligaments that are responsible for transferring the weight from the axial skeleton to the appendicular skeleton. The anterior sacroiliac Figure  7  Ligaments  of  Posterior  Sacrum Figure  6  Ligaments  of  Anterior  Sacrum
  16. 16. Lower Extremity Arthrology   16   ligaments are thin anterior parts of the fibrous capsule of the synovial part of the joint. Iliolumbar ligaments blend in with the anterior sacrospinous ligaments and radiate from transverse processes of L5 vertebra to the ilia. Posterior sacroiliac ligaments connect the PSIS with the lateral crests of the third and fourth segments of the sacrum and are very strong and tough. The short band of the posterior sacroiliac ligament also provides stability against all movements. Due to the posterior sacroiliac and interosseous sacroiliac ligaments running obliquely upward and outward from the sacrum, the axial weight pushing downward on the sacrum forces the ilia medially. This causes the sacrum to be compressed between the ilia and locks the irregular but congruent surfaces of the sacroiliac joints together. Iliolumbar ligaments act as accessory ligaments and assist in this mechanism. Sacrotuberous and sacrospinous ligaments offer secondary support posteriorly. They do not actually cross the joint, but they indirectly assist stabilization by resisting nutation. Stability is adequate for activities that involve relatively low static loading such as sitting and standing. For larger more dynamic loading, the SI joint is reinforced by ligaments and muscles. Nutation torque stretches many of the connective tissues at the SI joint. Increased tension in these ligaments further compresses the surface of the SI joint and thereby adds to their transarticular stability. In addition to ligaments, several hip and trunk muscles reinforce and stabilize the sacroiliac joints. Such muscles are erector spinae, lumbar multifidi, rectus abdominis, obliques abdominis internus and externus, transversus abdominis, gluteus maximus, latissimus dorsi, iliacus and piriformis. These muscles stabilize the SI joint by (1) generating active compressive forces against the articular surfaces, (2) increasing magnitude of nutation torque and subsequently engaging the active locking mechanism, and (3) pulling on connective tissues that reinforce the joints. As an example, let's consider erector spinae and bicep femoris. Erector spinae muscle will rotate the sacrum anteriorly and biceps femoris will rotate the ileum posteriorly and thus both of these actions create nutation. It is then safe to assume that anterior tilt of the pelvis will create counternutation. The muscles that create anterior tilt at the pelvis could create counternutation at the sacrum. Some of these muscles include iliopsoas, rectus femoris, tensor fascia latae, adductor longus, and pectineus.
  17. 17. Lower Extremity Arthrology Guide 17   Mechanical stability of the SI joint is provided by thoracolumbar fascia. Thoracolumbar fascia consists of three different layers that surround the posterior muscles of the lower back. Those layers are anterior, middle, and posterior. The anterior and middle layers are anchored medially to the transverse processes of the lumbar vertebrae and inferiorly to the iliac crest. The posterior layer covers the posterior surface of the erector spinae and latissimus dorsi muscle. The posterior layer attaches to the spinous processes of lumbar vertebrae, the sacrum, and the ilium, adding stability to the SI joint. Posterior layer stability to the joint is provided by erector spinae muscle creating a nutation torque by rotating the sacrum anteriorly and thus locking the joint and stabilizing it. Medial and posterior layers of thoracolumbar fascia fuse at their lateral margins and thus blend with internal oblique and transversus abdominis musculature. The internal oblique and transversus abdominis muscles compress the ilia toward the sacrum, increasing joint stability. Stability is further enhanced by the superficial attachments of latissimus dorsi and gluteus maximus to thoracolumbar fascia resulting in an increased compression of the SI joint. The iliacus and piriformis muscles provide secondary stability at the SIJ articulation by attaching directly to the capsule or margins of the SI joint. Pregnancy plays a large role in SI joint biomechanics in women. The release of relaxin during pregnancy decreases the intrinsic strength and rigidity of collagen. The action of relaxin is responsible for the softening of the ligaments supporting the SI joint and the symphysis pubis. This causes the joint to become more mobile, less stable and increase the size of pelvic outlet during childbirth. There is less resistance to these hormonal-induced changes due to the smoother articular surfaces of the SI joints of women being pregnant. Joint Configuration The SI joint is the articulation between the auricular surface of the sacrum and the ilium. SI joint is formed within sacral segments S1, S2 and S3. As mentioned previously the articular surface of the ilium is convex and faces anteriorly and inferiorly. The articulating surface of the sacrum is concave and faces more posterior and inferiorly compared to the ilium. The articulating surfaces on the sacrum are C-shaped and are located on the sides of the fused sacral vertebrae lateral to the sacral foramina. The SI joint consists of an anterior synovial joint and a posterior syndesmosis. The articular surfaces of this synovial joint have irregular but
  18. 18. Lower Extremity Arthrology   18   congruent elevations and depressions that interlock. The articulating surface of the sacrum is covered by hyaline cartilage. The ilium-articulating surface is covered by fibrocartilage. The overall mean thickness of the sacral cartilage is greater than that of the iliac cartilage. Ligaments of the Sacroiliac Ligaments Attachments Function Associated Constraints Anterior Sacroiliac 3rd sacral segment to the lateral side of the pre-auricular sulcus Primary source of stability; reinforce the anterior side of the SI joint Nutation Iliolumbar Tip and anteroinferior aspect of the transverse process of L5 to (1) the posterior margin of the iliac fossa and (2) to the iliac crest anterior to the sacroiliac joint Primary source of stability; reinforce the anterior side of the SI joint; stabilizes L5 on the ilium Nutation Interosseous Sacroiliac Deep portion: superior and inferior bands from depressions posterior to the sacral auricular surface to those on the iliac tuberosity Superficial: sheet connecting the poster superior margin posterior to the sacral auricular surface to the corresponding margins of the iliac tuberosity Forms part of the sacroiliac articulation (syndesmosis): binds the sacrum to the ilium; Primary source of stability Stability in all motions Posterior sacroiliac (short and long) Short: posterior- lateral side of the sacrum to the ilium, near the iliac tuberosity and the PSIS Long: 3rd and 4th sacral segments to PSIS Primary source of stability; reinforce the posterior side of the SI joint Short: all pelvic and sacral movement Long: Counternutation Sacrotuberous Posterior superior iliac spine (PSIS), lateral sacrum, and coccyx, attaching to the ischial tuberosity Secondary source of stability Nutation Sacrospinous Lateral margin of caudal end of sacrum and coccyx, attaching to the ischial spine Secondary source of stability Nutation Common Joint Pathology Osteoarthritis. As with most other joints in the body, the SI joints have a cartilage layer covering the bone. When this cartilage is damaged or worn away osteoarthritis may occur. This could cause severe pain and discomfort for the patient. As the condition progresses at the SI joint, the joint cleft narrows and osteophytes may form within the ligaments. These osteophytes could ossify the ligaments and fuse the sacrum to the ilium and cause complete immobilization of the SI joint. Parturition-Induced SIJ Pain. Laxity of the sacroiliac joint could also cause symptomology. Women are more likely to experience this than men because of childbearing. During childbirth, release of relaxin and progesterone cause more mobility and an increase in synovial fluid. Hypermobility and ligament laxity could cause increased risk of injury such as dislocation and pelvic girdle pain postpartum.
  19. 19. Lower Extremity Arthrology Guide 19   Ankylosing spondylitis. Ankylosing spondylitis is an inflammatory condition of the joints, especially in the spinal column. Inflammation within joints can lead to severe pain and discomfort. In very severe cases the inflammation can induce fibrosis and cause the bones to fuse, resulting in massive restrictions to mobility. Typical patient complaints are persistent low back pain and stiffness that is worse in the morning and night, but improves with activity. Patients often complain of unilateral or alternating buttock pain. Also, patients tend to complain of pain during the second half of sleep only. Differential diagnosis for ankylosing spondylitis include stress fracture, muscle spasm, lumbar disk herniation, osteoarthritis, gout, cancer, infection, and rheumatoid arthritis. The disease most commonly presents in young males, ages 15-30 years old. Femoroacetabular Joint Overview The femoroacetabular (FA) joint, more commonly known as the hip joint is a ball and socket joint and is created with an articulation between the femoral head and the socket of the acetabulum on the pelvis with three degrees of freedom. Three bones of the pelvis; the ischium, ilium, and pubis form the acetabulum. The femur is the longest and strongest bone in the body. The femoral head projects medially and slightly anteriorly for an articulation with the acetabulum. The femoral head is secured within the acetabulum by an extensive set of connective tissues and muscles. Thick layers of articular cartilage, muscle, and cancellous bone in the proximal femur help reduce the large forces that cross the joint. The hip is required to operate in both open and close kinetic chain and so stability is very important at this joint. The stability to the joint mostly comes from the joint configuration as well as the ligamentous design. Muscles also contribute to joint stability as the joint must withstand high loads during activity such as running, jumping, and walking. Neurovasculature. The femoroacetabular joint receives its blood supply from the artery to the head of the femur, but the primary blood supply to the joint Figure  8  Femoroacetabular   Joint  Surfaces Figure  9  Bones  of  Acetabulum
  20. 20. Lower Extremity Arthrology   20   comes from the medial and lateral circumflex femoral arteries, which come off the deep femoral artery. The joint is also highly innervated as the sacral and lumbar plexus are close in proximity to it and provide numerous innervating branches. The joint gets innervations from femoral nerve (anteriorly), obturator nerve (inferiorly), nerve to quadratus femoris (posterior), and the superior gluteal nerve (superior). Tissue Layers • Integumentary o Epidermis o Dermis o Hypodermis • Subcutaneous tissue o Fascia lata o Subcutaneous adipose tissue • Muscle o Anterior compartment § Pectineus § Iliopsoas § Rectus femoris § Sartorius o Medial compartment § Adductor longus § Adductor brevis § Adductor magnus § Gracilis § Obturator externus o Posterior compartment § Semitendinosus § Semimembranosus § Biceps femoris (long head) o Gluteal region § Gluteus maximus § Gluteus medius § Gluteus minimus § Tensor fasciae latae § Piriformis § Obturator internus § Superior gemellus § Inferior gemellus § Quadratus femoris • Ligaments and joint capsule • Joint articular surfaces and deep ligaments    
  21. 21. Lower Extremity Arthrology Guide 21   Joint Motions Biomechanics Since the hip is a ball and socket joint, it is capable of a variety of motions in different planes. The femoral head is convex and the acetabular socket is concave. The hip joint is capable of working in both open chain and closed chain positions. In open chain, the femur tends to move on the pelvis in order to create motion. Since the femur is moving on the pelvis, the convex is moving on the concave, the roll and glide of the femoral head are in opposite directions. The hip has 120 degrees of flexion in the sagittal plane when the femur spins around the mediolateral axis. In the frontal plane of open chain movement, the hip has about 40 degrees of abduction and 25 degrees beyond the neutral line of adduction around the anteroposterior axis. The femur will roll superior and glide inferior for abduction and will roll inferior and glide superior for adduction. In the sagittal plane, the hip also has 20 degrees of extension with the femur spinning around the mediolateral axis. Finally, in the transverse plane, the femur Joint Motion Primary Movers Secondary Movers Flexion Iliopsoas, Sartorius, Tensor fasciae latae, Rectus femoris, Adductor longus, Pectineus Adductor brevis, Gracilis, Gluteus minimus (anterior fibers) Extension Gluteus maximus, Biceps femoris (long head), Semitendinosus, Semimembranosus, Adductor magnus (posterior head) Gluteus medius (posterior fibers), Adductor magnus (anterior head) Abduction Gluteus medius, Gluteus minimus, Tensor fasciae latae Piriformis, Sartorius Adduction Pectineus, Adductor longus, Gracilis, Adductor brevis, Adductor magnus Biceps femoris (long head), Gluteus maximus (lower fibers), Quadratus femoris Internal rotation NA Gluteus minimus (anterior fibers), Gluteus medius (anterior fibers), Tensor fasciae latae, Adductor longus, Adductor brevis, Pectineus External rotation Gluteus maximus, Piriformis, Obturator internus, Superior gemellus, Inferior gemellus, Quadratus femoris Gluteus medius (posterior fibers), Gluteus minimus (posterior fibers), Obturator externus, Sartorius, Biceps femoris (long head) Figure  10  Muscle  Actions  at  Sacroiliac  Joint
  22. 22. Lower Extremity Arthrology   22   can rotate internally about 35 degrees and externally about 45 degrees around the long axis of the femur. During external rotation, the femoral head rolls posteriorly and glides anteriorly and during internal rotation the femoral head rolls anterior and glides posterior. In closed chain, the arthrokinematics flip as the roll and glide of the acetabulum on the femur are in the same direction because the concave surface is moving on the convex surface. The pelvis may also move in all three planes around all three axes, although the motions have different names, and there is a smaller range available. In the frontal plane in closed chain, the pelvis can abduct away from the femur about 30 degrees and adduct toward the femur about 20 degrees from neutral around the anteroposterior axis. In closed chain, a superior roll and glide creates abduction, while an inferior roll and glide creates adduction. In the sagittal plane, the pelvis is capable of anteriorly tilting 30 degrees, and posteriorly tilting 15 degrees by spinning around the mediolateral axis. Finally, in the horizontal plane, the pelvis can internally and externally rotate about 15 degrees in each direction, with a total arc of 30 degrees of motion around the transverse axis. During internal rotation, the acetabulum must anteriorly roll and glide. The opposite is true to create external rotation The FA joint has very complex biomechanics. Motion that occurs at the hip joint occurs either in open chain or in closed chain. In open chain the femur moves on the acetabulum, but in closed chain the acetabulum moves on the femur. Let's take hip flexion for example, we can take our thigh into flexion while keeping the pelvis stable, this constitutes as open chain. Closed chain hip flexion would occur when the trunk moves into flexion while keeping the lower limb stable. When considering movement done on a stable pelvis, we must consider lumbopelvic rhythm due to the close relationship between the hip and the lumbar spine. The movement that occurs is in the sagittal plane and is considered to be either ipsidirectional lumbopelvic rhythm or contradirectional rhythm. Ipsidirectional lumbopelvic rhythm describes a movement in which the lumbar spine and pelvis rotate in the same direction amplifying overall trunk motion. An example of this motion would be reaching down to pick something from the ground. Contradirectional rhythm describes a movement in which the lumbar spine and pelvis rotate in opposite direction. This type of movement is important as it allows for separation of the pelvis and lumbar spine during activities where the head and neck need to maintain neutral
  23. 23. Lower Extremity Arthrology Guide 23   position. Other motions that occur in closed chain are anterior and posterior pelvic movements. Pelvic tilting is defined based on the position of the anterior superior iliac spine (ASIS) of the pelvis. When the ASIS moves anterior and inferior, it is considered an anterior pelvic tilt and results in hip flexion. When the ASIS moves posterior and superior, it is considered a posterior pelvic tilt and results in hip extension. Since the hip is a ball and socket joint there is three degrees of freedom and thus mobility will be influenced by muscular activation. We will first discuss hip flexion of the joint. Iliopsoas, sartorius, tensor fascia latae, rectus femoris, adductor longus, and pectineus are all considered to be primary hip flexors in an open chain position. The main hip flexor muscles out of these would have to be iliopsoas due to its large size, line of pull, and cross-sectional area. The iliopsoas tendon averts posteriorly to its distal attachment. In full hip extension, this increases the tendon's angle of insertion creating an optimal line of pull. The secondary hip flexors (adductor brevis, gracilis, and the anterior fibers of gluteus minimus) do not have direct lines of pull into hip flexion, but they can produce some force in that direction. Additionally, any muscle that is considered a hip flexor in the open chain position can also produce an anterior pelvic tilt in closed chain. An anterior pelvic tilt is also achieved by force coupling that occurs between the hip flexors and back extensors on a fixed femur. In the open chain position, gluteus maximus, the hamstrings (biceps femoris (long head), semitendinosus, and semimembranosus), and the posterior head of the adductor magnus are considered to be primary hip extensors. Gluteus maximus is considered to be the primary hip extensor due to its large cross sectional area, line of pull, and moment arm. Adductor magnus (posterior part) is also considered to be a primary mover due to its large moment arm. It is at 70 degrees at hip flexion and beyond that most adductors (exception to pectineus) are capable of assisting with hip extension. The hamstring group is also primary mover due to the line of pull and large moment arm. All three of those muscles are considered to be the primary movers for hip extension. The posterior fibers of the gluteus medius and the anterior head of the adductor magnus are secondary movers into hip extension. Neither one of these muscles has a great line of pull into extension from the anatomical position. Additionally, the posterior fibers of gluteus medius do not have as much cross sectional area as the other hip extensor muscles. Similar to the hip flexors, the hip extensors in open chain are all capable of producing a
  24. 24. Lower Extremity Arthrology   24   posterior pelvic tilt in closed chain. A force couple between the abdominal muscles and the hip extensors creates this motion. Additionally, the hip extensors are responsible for eccentrically controlling a forward lean of the body. The primary extensor muscle group that is responsible for this is the hamstrings. As the body leans forward the displacement of body weight moves farther in front of the hips requiring a greater activation from the hamstrings. This is because the moment arm of the gluteus maximus is decreased as the hip flexes, but the moment arm of the hamstrings is increased. The primary movers into hip adduction are pectineus, adductor longus, gracilis, adductor brevis, and adductor magnus. The adductors also are able to work in all three planes; not just the frontal plane. This largely has to do with their distal attachment not being located precisely in midline. The biceps femoris (long head), gluteus maximus (lower fibers), and quadratus femoris are all considered to be secondary movers into adduction because some of their fibers have a line of pull in this direction so they can produce some amount of force into adduction. Adductors also assist in internal rotation of the hip joint. The primary hip abductors are the gluteus medius, gluteus minimus, and tensor fasciae latae. The secondary abductors of the hip joint are considered to be the piriformis and sartorius. Gluteus medius is considered the main hip abductor. The distal attachment of gluteus medius causes it to have the largest moment arm of all the other abductors. Gluteus medius also has the largest cross sectional area out of all the other abductors making it the primary mover in abduction. Gluteus minimus occupies 20% of the total abductor moment. Tensor fasciae latae occupies 11% of total abductor moment. The hip abductors also contribute to hip internal rotation. The abductor torque produced by the hip abductor muscles is essential to the control of the frontal plane pelvic-on-femoral kinematics during walking. During the stance phase the hip is stabilized over the relative fixed femur by the hip abductors. The hip abductors also play a crucial role during the single-limb support phase of gait. Without adequate torque on the stance limb, the pelvis and the trunk may drop toward the side of the swinging limb. The Figure  11  Trendelenburg  Sign
  25. 25. Lower Extremity Arthrology Guide 25   observation of a contralateral hip drop during gait is known as a Trendelenburg gait pattern, and is due to lack of strength or control of the abductor muscles. External rotation of the hip is done by gluteus maximus, piriformis, obturator internus, superior gemellus, inferior gemellus, and quadratus femoris. Gluteus maximus has the largest cross-sectional area and so is considered the primary external rotator of the hip. The others have fairly small cross-sectional areas but have a direct line of pull and they provide stability to the posterior aspect of the joint. The gluteus medius (posterior fibers), gluteus minimus (posterior fibers), obturator externus, sartorius, and biceps femoris (long head) are all secondary movers into external rotation, due to their indirect lines of pull. Hip external rotators are most functional during closed chain movements such as cutting, pivoting, and changing direction very rapidly. The external rotators can also function in open chain movements. Open chain external rotation of the hip will rotate the foot so the toes point more laterally and the heel is more medial. The last motion produced by the hip is internal rotation. There are no primary internal rotators of the hip. This is due to the need of muscles to be oriented in a horizontal plane of motion during standing and that does not occur. There are many secondary hip internal rotators, though. Secondary movers are gluteus minimus (anterior fibers), gluteus medius (anterior fibers), tensor fasciae latae, adductor longus, adductor brevis, and pectineus. As the hip moves from 0 degrees to 90 degrees of flexion, the line of pull and moment arm of many of these muscles becomes more optimally oriented to create internal rotation at the hip. As the hip moves into 90 degrees of flexion, some external rotators change their action and assist with internal rotation. Joint Configuration During weight bearing the hip must translate immense loads; its closed kinetic chain kinematics help it provide stability. To promote congruency and stability the acetabular socket of the hip joint is fairly deep. The acetabular labrum also helps promote stability as it deepens the socket of the joint by an additional 30%. The labrum also forms a seal around the joint to maintain negative intra-articular pressure and thus create suction that prevents distraction of the joint. The seal also holds the synovial fluid within the joint and enhances the
  26. 26. Lower Extremity Arthrology   26   lubrication of the joint and its ability to dissipate load. The acetabulum and the femoral head also have thick layers of articular cartilage to prevent wear and tear of the joint surfaces. The bony anatomy of the hip is somewhat variable and may affect how the joint can function. Two measurements of the femur are considered: the angle of inclination and femoral torsion. The angle of inclination occurs in the frontal plane between an axis through the femoral head and neck and the longitudinal axis of the femoral shaft. At birth, the angle of inclination is about 140 to 150 degrees. Due to loading across the femoral neck, the angle reduces to 125 degrees near adulthood. When the angle of inclination varies greatly from typical, it is referred to either as coxa vara or coxa valga. When the angle is less than 125 degrees it is described as coxa vara and can lead to genu valgum at the knee. An angle greater than 125 degrees is considered to be coxa valga and can lead to genu varum at the knee. These varying conditions of the angle of inclination are illustrated in Figure 12. Femoral torsion occurs in the transverse plane between an axis through the femoral head and neck and an axis through the distal femoral condyles. At birth, the healthy infant is born with about 40 degrees of femoral torsion. By age 16 this angle decreases due to bone growth, muscular activity, and weight bearing. Typically, the femoral head sits 15 degrees anterior to the mediolateral axis, running through the femoral condyles. This is known as normal anteversion. Any rotation greater than 15 degrees anterior to the mediolateral axis is described as excessive anteversion, and is associated with in toeing at the foot. Conversely, an femoral torsion less than 15 degrees is described as retroversion and is associated with toe-out at the foot. Measurements at the acetabulum should also be noted. There are two commonly used measurements to describe the extent to which the acetabulum covers and secures the femoral head: center-edge angle and acetabular anteversion angle. The center-edge angle describes the position of the acetabulum and the amount of coverage it provides over the femoral head. A normal center-edge angle is approximately 35 degrees. Any significant decrease in this angle will decrease the coverage of the femoral head, Figure  13  Angle  of  Inclination Figure  12  Femoral  Torsion
  27. 27. Lower Extremity Arthrology Guide 27   and therefore predispose the hip to dislocations. The acetabular anteversion angle measures the extent to which the acetabulum projects anteriorly in relation to the pelvis. Normally, acetabular anteversion is about 20 degrees. When a hip demonstrates excessive acetabular anteversion, the anterior portion of the femoral head is exposed. When the angle is severe, the hip is more prone to dislocation and labral lesions. The open packed position of the hip joint is in 30 degrees of flexion, 30 degrees of abduction, and slight external rotation. The closed packed position is with the hip in full extension, combined with slight external rotation and abduction. The hip also has a variety of ligaments that attach to restrain certain movements and help keep the joint stable. The primary ligaments of the joint are iliofemoral, pubofemoral, and ischiofemoral ligaments. All three of these ligaments blend with the joint capsule and are taut in extension. Out of the three, the iliofemoral ligament is the strongest. In standing posture, the femoral head moves anteriorly and pushes against the iliofemoral ligament. Iliofemoral ligament is also taut in external rotation. The pubofemoral ligament is taut in hip abduction and external rotation. The ischiofemoral ligament is the opposite, and is taut in hip adduction and internal rotation. Knowledge of these ligaments is useful therapeutically during attempts to stretch the entirely of the hip capsule. With full hip extension, combined with slight internal rotation and abduction, twists most of the ligaments into their taut position and so this is called closed packed position. The opposite of this position would be to the open packed position of the hip joint is in 30 degrees of flexion, 30 degrees of abduction, and slight external rotation. The ligamentum teres and transverse acetabular ligament also stabilize the hip. The ligamentum teres runs from the head of the femur directly to the acetabular fossa, which helps to maintain the alignment of the femoral head in the fossa. The transverse acetabular ligament completes the acetabular ring, reinforcing the inferior aspect of the joint. Ligaments of the Femoral Acetabular Ligaments Attachments Function Associated constraints of the joint Iliofemoral Anterior inferior iliac spine, intertrochanteric line of the femur Reinforces the joint capsule Limits extension of the femur Ischiofemoral Ischium posterior to the acetabulum, greater trochanter, iliofemoral ligament Reinforces the joint Assists iliofemoral ligament in limiting extension of the femur Pubofemoral Iliopubic eminence, superior pubic ramus, fibrous joint capsule Reinforces the joint capsule Limits abduction of the femur
  28. 28. Lower Extremity Arthrology   28   Ligamentum teres Fovea of the femoral head, acetabular notch Attaches the femoral head to the acetabular fossa Prevents distraction/dislocation of the femoral head from the acetabulum Transverse acetabular Margins of the acetabular notch Completes the inferior part of the acetabulum Resists caudal translation of the femoral head Common Joint Pathology Femoroacetabular impingement (FAI). In FAI, bone spurs develop around the femoral head and/or along the acetabulum. The bone overgrowth causes the hipbones to hit against each other rather than to move smoothly. Over time, this can result in the tearing of the labrum and breakdown of articular cartilage (osteoarthritis). There are three types of FAI: pincer, cam, and combined impingement. Pincer type of impingement occurs because extra bone extends out over the normal rim of the acetabulum. The labrum can be crushed under the prominent rim of the acetabulum. Pincer type is more common in females. In cam impingement the femoral head is not round and cannot rotate smoothly inside the acetabulum. A bump forms on the edge of the femoral head that grinds the cartilage inside the acetabulum. Cam impingement is more common in males. Combined impingement occurs when both pincer and cam types are present, which is common. Impingement is most typically felt in hip flexion, adduction and external rotation. People with FAI usually have pain in the groin area, although the pain may be lateral to the groin. Patients may complain of a dull ache or sharp stabbing pain with turning, twisting, and squatting. Labral tears. FAI, trauma or arthritis can all result in labral tears. Planting the leg on the ground and twisting usually is a cause of traumatic tears. Major trauma such as motor vehicle accidents can also tear the labrum. As people develop arthritis; they can also develop labral tears. Patients usually complain of clicking, pain, feeling of giving out, symptoms get worse with prolonged walking, standing, sitting. Osteoarthritis. In osteoarthritis, the cartilage in the hip joint gradually wears away over time. As the cartilage wears away, it becomes frayed and rough and the protective joint space between the bones decreases. This can result in bone Figure  14  Hip  FAI Figure  15  Hip  Osteoarthritis
  29. 29. Lower Extremity Arthrology Guide 29   rubbing on bone. To make up for the lost cartilage, the damaged bones may start to grow outward and form bone spurs (osteophytes). Osteoarthritis develops slowly and the pain worsens over time and is most common in people over the age of 50, though younger people are affected by it also. The most common symptom of hip osteoarthritis is pain around the hip joint. Usually pain has a slow onset, but it may have a sudden onset. Pain and stiffness may be worse in the morning or after sitting for a long period of time. Over time, painful symptoms may occur more frequently including during rest or at night. Patients with OA can also present with limited range of motion especially into internal rotation and flexion. Hip fractures. Fractures are a very serious and common issue in the United States. The most common mechanisms of injury for hip fractures are falls and collisions. The older population is more affected by this and unfortunately the incidence may continue to rise due to the increased life expectancy. The patient with a hip fracture will have pain over the outer upper thigh or in the groin. There will be significant discomfort with any attempt to flex or rotate the hip. Fractures are usually treated with surgery. The type of surgery used to treat a hip fracture is primarily based on the bones and soft tissues affected or on the level of the fracture. Approximately 40% of those with a hip fracture are able to perform their daily functioning needs however; about half will continue to use an assisted device for walking.
  30. 30. Lower Extremity Arthrology   30   Knee Joint Complex Introduction The knee joint is formed by articulations between the patella, femur and tibia (Figure 16). The knee is the largest joint and the most frequently injured joint in the body. The tibiofemoral portion of the knee joint is a hinge type synovial joint. It is the most complex diarthrosis of the body. The knee primary motions include flexion and extension with some external and internal rotation. The knee is overall mechanically referred to as a weak joint. The stability and strength of this joint is fully dependent on the strength of the muscles and tendons surrounding joint entirety, as well as the ligaments connecting the tibia and the femur. The knee has up to 14 bursae of various sizes in and around the knee joint complex. Bursae help provide an extra amount of friction control for the joint to move fluidly. Bursae around the patella include the prepatellar bursa, the superficial and deep infrapatellar bursae, and the suprapatellar bursa. Bursae of the complex that are not in close anatomical proximity to the patella include the pes anserine bursa, the iliotibial bursa, the tibial and fibular collateral ligament bursae and the gastrocnemius-semimembranosus bursa. These fluid filled sacs cushion the joint and reduce friction between muscles, bones, tendons and ligaments. The knee is important biomechanically during walking. In the stance phase, the knee is slightly flexed. This allows shock absorption, energy conservation, and transmission of forces to the lower limb. In swing phase, the knee is flexed in order to shorten the functional length of the lower limb, which helps the foot clear the ground. Gait has functional requirements of both stability and mobility for the knee to allow proper energy- efficient and safe propulsion over ground. Figure  16  Knee  Joint  Articulations
  31. 31. Lower Extremity Arthrology Guide 31   Muscles of the Knee Joint Complex Muscles Proximal attachment Distal attachment Action Segmental Innervation Peripheral innervation Sartorius anterior superior iliac spine medial aspect of the proximal tibia flexes and assists internal rotation of the knee (L2-3 [4]) Femoral nerve Rectus femoris anterior inferior iliac spine and groove superior to the acetabulum the base of the patella extends knee (L2-3-4) Femoral nerve Vastus intermedius anterior aspect of the proximal 2/3rds of the femoral shaft lateral border of the patella actions- extends knee Extends knee (L2-3-4) Femoral nerve Vastus lateralis Intertrochanteric line, greater trochanter, gluteal tuberosity and linea aspera Base and lateral border of the patella Extends knee (L2-3-4) Femoral nerve Vastus medialis Intertrochanteric line, spiral line, linea aspera and medial supracondylar line Base and medial border of the patella Extends knee (L2-3-4) Femoral nerve Tensor fasciae latae ASIS & external lip iliac crest iliotibial tract assists in maintaining knee extension (L4-5-S1) Superior gluteal nerve Gracilis body of the pubis & inferior pubic ramus medial surface of tibia, distal to condyle, proximal to insertion of semitendinosus, lateral to insertion of sartorius flexes & medially rotates the knee (L2-3-4) Obturator nerve Biceps femoris ischial tuberosity & sacrotuberous lig. (long head) ; lateral lip of linea aspera & lateral supracondylar line (short head) lateral side of fibular head Both heads: Flex knee Long Head: Extends hip Long head: (L5-S1-2-3) Short head: (L5-S1-2) Long head: tibial branch of sciatic nerve Short head: Fibular branch of sciatic nerve Semimembr anosus Posterior aspect of the medial tibial condyle posterior aspect of the medial tibial condyle Ischial tuberosity (L4-5-S1-2) Tibial division of the sciatic Semitendin osus ischial tuberosity proximal, medial tibia flexes & medially rotates knee (L4-5-S1-2) Tibial division of the sciatic Gastrocnem ius posterior aspect of the condyles and joint capsule Posterior calcaneal surface flexes knee (S1-2) Tibial nerve Popliteus lateral femoral condyle and oblique popliteal ligament Soleal line of the tibia In NWB, IR of tibia and knee flexion; in WB insertion is fixed: ER of femur and knee flexion; unlocks the knee from extension into early flexion (L4-5-S1) Tibial nerve Articularis Genu Distal anterior shaft of femur Proximal portion of synovial membrane of knee joint Pulls articular capsule proximally (L2-3-4) Femoral
  32. 32. Lower Extremity Arthrology   32   Tibiofemoral Joint Overview The tibiofemoral joint is formed by the condyles of the femur and the tibial plateau. The joint is a modified hinge joint with two degrees of freedom. The primary motion is flexion and extension in the sagittal plane. Some internal and external rotation can occur with slight flexion of the knee. The quadriceps femoris is considered to be the most important muscle for stabilization of the tibiofemoral joint. The knee is considered most stable in a fully extended position. This is the position where the femur’s contact on the tibia, is most congruent and the ligaments associated with the tibiofemoral joint are the most taut. In this position, many of the tendons surrounding the joint act as supporting structures as well. Neurovasculature. There are 10 vessels that come together to form the periarticular genicular anastomoses around the knee to supply blood to the knee joint. These 10 vessels include: genicular branches of the femoral, popliteal, and anterior and posterior recurrent branches of the anterior tibial recurrent and circumflex fibular arteries. Other supporting features of the tibiofemoral joint including the joint capsule, the cruciate ligaments, the outer portions of the menisci, and the synovial membrane are supplied by the middle genicular branches of the popliteal artery. The tibiofemoral is innervated by all the nerves supplying the muscles that cross the knee joint. Branches from the femoral nerve innervate the anterior aspect of the knee. The tibial nerve supplies the posterior aspect, and the common fibular nerve innervates the lateral aspect. Articular branches from both the obturator and saphenous nerves supply the medial aspect of the knee. Tissue Layers • Skin o Epidermis o Dermis o Hypodermis • Superficial fascia (fascia lata) o Subcutaneous tissue • Deep fascia • Muscles and tendons o Quadriceps femoris § Rectus femoris § Vastus lateralis § Vastus medialis § Vastus intermediate
  33. 33. Lower Extremity Arthrology Guide 33   o Hamstrings § Biceps femoris § Semimembranosus § Semitendinosus o Gracilis o Sartorius o Gastrocnemius o Popliteus o Iliotibial band • Vascular supply o Popliteal artery o Descending genicular o Anterior tibial recurrent artery o Posterior tibial recurrent artery o Circumflex fibular artery o Inferior medial genicular artery o Inferior lateral genicular artery o Middle genicular artery o Superior medial genicular artery o Superior lateral genicular artery • Innervation o Obturator o Femoral o Tibial o Common fibular o Saphenous o Nerve to the popliteus o Nerve to gastrocnemius • Ligaments o Medial collateral ligament o Lateral collateral ligament o Oblique popliteal ligament o Arcuate popliteal ligament o Coronary ligament o Transverse ligament of the knee o Meniscofemoral ligament • Fibrous joint capsule o Synovial membrane o Ligaments § Anterior cruciate ligament § Posterior cruciate ligament o Menisci § Medial menisci § Lateral menisci o Bursa § Prepatellar bursa § Suprapatellar bursa § Superficial infrapatellar bursa § Deep infrapatellar bursa § Semimembranosus bursa § Pes anserine bursa
  34. 34. Lower Extremity Arthrology   34   o Plicae § Suprapatellar plica § Infrapatellar plica § Medial plica o Fat pads § Infrapatellar fad pad o Synovial fluid o Articular cartilage Joint Motions Motion Primary Movers Secondary Movers Degrees Possible Knee flexion Hamstrings (semitendinosus, semimembranosus, long head of the biceps); short head of the biceps Gracilis, sartorius, gastrocnemius, popliteus 135 degrees Knee extension Quadriceps femoris Weakly: tensor of fascia lata 0 degrees, hyperextension may be available up to 10-15 degrees Knee external rotation Biceps femoris when the knee is in a flexed position NA 40 degrees; may be difficult to establish neutral rotation Knee internal rotation Semitendinosus and semimembranosus when knee is flexed; popliteus when non-weight bearing and with the knee extended Gracilis, sartorius 30 degrees; may be difficult to establish neutral rotation Biomechanics and Joint Configuration The tibiofemoral joint primary motions are flexion and extension; which occur about the mediolateral axis of rotation. The range of motion of the knee is 130 to 150 degrees of knee flexion and 5 to 10 degrees of knee extension beyond neutral position. External and internal rotation of the knee occurs about a longitudinal axis of rotation. These rotations increase with knee flexion. At 90 degrees of knee flexion, the knee can rotate internally about 30 degrees and externally at about 45 degrees. Beyond 90 degrees of flexion, rotation decreases due to limitations by soft tissues. An important concept, which helps with the stability of the knee, is the screw home mechanism. During the last portion of active range of motion into extension a rotation between the tibia and the femur occurs. This rotation produces the screw home mechanism, or “locking” of the knee. The rotation happens during the last 30 degrees of knee extension. Anterior tibial glide persists on the tibia's medial condyle because its articular surface is longer in that dimension than the lateral condyle. Prolonged anterior glide on the medial side produces external
  35. 35. Lower Extremity Arthrology Guide 35   tibial rotation. There are three factors that affect the rotation mechanism; the shape of the medial femoral condyle, the passive tension of the anterior cruciate ligament, and the lateral pull of the quadriceps muscle. This rotation is not under voluntary control. This helps the knee’s stability for standing upright. The screw-home mechanism decreases the work of the quadriceps femoris muscle. The muscle can relax once the knee joint is fully extended. To unlock the extended knee, the joint internally rotates first. The popliteal muscle rotates the femur externally or rotates the tibia internally to initiate flexion from a fully extended starting position. The distal femoral condyles create a convex surface and the proximal tibial plateau creates concave surface. The tibial condyles slide posteriorly on the femoral condyles during flexion, and slide anteriorly during extension. In unloaded movement, open chain, the concave surface will glide in the same direction of the rotation. In loaded movement, closed chain, the convex surface will glide in the opposite direction of the rotation. The medial meniscus has an oval shape (Figure 17) and it attaches to the deep layer of the medial collateral ligament and capsule. The lateral meniscus has circular shape and it attaches only to adjacent capsule. The quadriceps and semimembranosus attach to both menisci and the popliteus attaches only to the lateral meniscus. These muscles help to stabilize the menisci. Neurovasculature supply of the menisci is greatest at the external borders, while the internal border has no blood and nerve supply. The menisci are designed to absorb shock, therefore, they reduce the compressive stress across the joint. During walking the compressive forces at the joint reach 2.5-3x the body weight and increase to 4x the body weight with stair climbing. The menisci help to reduce the pressure on the articular cartilage by increasing the contact area, which protects the knee joint. In addition, it also increases stability of the knee by deepening the tibial plateaus, decreasing friction by 20%, and increasing contact area by 70%. Increasing the contact area helps to disperse force over a greater surface area, and decrease the total force experienced by any one point in the joint. The menisci serve a vital role in maintaining the integrity and functionality of the tibiofemoral joint. Figure  17  Tibial  Plateau  Anatomy
  36. 36. Lower Extremity Arthrology   36   The ligaments that surround the knee are important in stabilizing the knee. The cruciate ligaments also guide the knee in natural arthrokinematics by creating tension, and contribute to the proprioception of the knee. The anterior cruciate ligament (ACL) runs from posterior femur to anterior side of the tibia (Figure 18). Its tension changes as the knee flexes and extends. The anteromedial bundle is taut in flexion and the posterolateral bundle is taut in extension. It is mainly taut as the knee reaches to full extension. The posterior cruciate ligament (PCL) runs from the posterior intercondylar area of the tibia to the lateral side of the medial femoral condyle (Figure 18). Most fibers of this ligament become taught with increasing knee flexion. Tension peaks between 90 and 120 degrees of knee flexion. The primary role of the collateral ligaments is to limit excessive motion of the knee in the frontal plane. The ligaments also play a role in providing resistance to extreme external and internal rotation of the knee. The medial collateral ligament (MCL) is a flat, broad ligament (Figure 19). It had two layers, superficial and deep, the run from the femur to the tibia and the medial meniscus. The superficial fibers blend with the medial patellar retinaculum fibers. The deep fibers attach to the posterior-medial joint capsule, medial meniscus, and tendon of the semimembranosus muscle. The MCL resists valgus force. Since the deeper fibers are shorter, they are more commonly injured than the superficial fibers during excessive valgus trauma. The lateral collateral ligament (LCL) is a round ligament that runs from the lateral epicondyle of the femur and the head of the fibula (Figure 20). The LCL does not attach to the lateral meniscus. It resists varus force. Figure  18  Ligamentous  Contribution  to  Knee Figure  19  Medial  Collateral   Ligaments Figure  20  Lateral  Collateral  Ligament
  37. 37. Lower Extremity Arthrology Guide 37   The knee has a crucial role during gait. During heel contact, the knee is in 5 degrees of flexion and it continues to flex to 15 or 20 degrees during loading response. The quadriceps eccentrically control this flexion. This helps with weight acceptance as the weight of the body shifts to the lower extremity. After slight flexion, the knee extends until heel off. The knee then begins to flex again to 35 degrees during toe off. By mid swing knee flexion reaches a maximum knee flexion of 60 degrees. This knee flexion is to shorten the length of the lower limb and assist toe clearance. In mid and terminal swing the knee extends again. During gait, the knee requires range of motion from full knee extension to 60 degrees of knee flexion. Gait impairments are noted when a lack of knee range is available. A lack of knee flexion and extension will impair toe clearance and functional length. Ligaments of the Tibiofemoral Ligament Proximal attachment Distal attachment Function Anterior cruciate ligament (ACL) posterior femur anterior side of the tibia Resist extension Resist extremes of varus, valgus, and axial rotation Posterior cruciate ligament (PCL) anteroinferior femur posterior side of the tibia Resist knee flexion Resist extremes of varus, valgus, and axial rotation Lateral collateral Ligament (LCL) Femur Fibula resist varus resist knee extension resist extremes of axial rotation Medial collateral ligament (MCL) Femur *Two layers (deep and superficial) Tibia and the medial meniscus Resist valgus Resist knee extension Resists extremes of axial rotation Oblique popliteal ligament Tendon of the Semimembranosus Posterior lateral condyle of the femur Stabilizes the posterior aspect of the knee joint Limits external rotation of the tibia Transverse ligament of the knee Anterior edge of menisci crosses anterior intercondylar area holds menisci together during knee movement Coronary ligament of the knee Inferior edges of the medial lateral menisci to the joint capsule of the knee limiting rotation of the knee stabilizes medial and lateral menisci Arcuate popliteal ligament Posterior fibular head posterior surface of the knee reinforces posterior lateral joint capsule Meniscofemoral ligament: 1. Anterior 2. Posterior Posterior horn of the lateral meniscus Extends from the posterior horn of lateral meniscus Distal edge of the femoral PCL Medial femoral condyle Stabilizes the lateral meniscus
  38. 38. Lower Extremity Arthrology   38   Common Joint Pathology Knee Fracture. With injury to the knee, it is important to rule out a suspected fracture. There are two prediction rules for use in determining the need for a radiograph of the knee; the Ottawa Knee Rules, and the Pittsburgh Knee Rules. Ottawa Knee Rules • age 55 or older • isolated tenderness of the patella • tenderness over the fibular head • inability to flex knee >90 degrees • inability to weight bear immediately, or in the emergency room for 4 steps Pittsburgh Knee Rules • Blunt trauma or fall as the mechanism of injury as well as either of the following: • older than 50 years or younger than 12 years • inability to walk 4 weight bearing steps in the emergency department Medial Collateral Ligament Injuries (MCL). The most common mechanism of injury to MCL is a force to the lateral aspect of the knee, creating a valgus force and placing strain on the MCL. This ligament may also be injured by a rotational stress at the knee. In order to test for this injury, a valgus stress test can be completed in both full extension and in 25-30 degrees of knee flexion. If there is laxity in the full extension position, this indicates a possible sprain of the MCL, the cruciate ligaments, or the medial capsule. If there is laxity in 25-30 degrees of flexion, this indicates an MCL sprain specifically. Most injuries to the MCL can be managed non- operatively with bracing due to the good blood supply to the MCL. Lateral Collateral Ligament Injuries (LCL). This ligamentous injury is much less common than injury to the MCL. The most common mechanism of injury is a force to the medial aspect of the knee, creating a varus force and placing strain on the LCL. This injury is rarely isolated and may also cause injury to the cruciate ligaments and knee joint capsule. In order to test for this injury, a varus stress test can be completed in both full extension and in 25-30 degrees of knee flexion. If there is laxity in knee full extension, it may indicate damage to
  39. 39. Lower Extremity Arthrology Guide 39   the LCL, cruciate ligaments, or lateral capsule. If there is laxity of 25-30 degrees of knee flexion, it indicates specifically an LCL sprain. Apley’s distraction test and the dial test are other tests that can also be completed. With this injury, it is important to rule out fibular nerve injury due to the close location of the fibular nerve. The LCL does not have a good blood supply and may need surgical repair. Anterior Cruciate Ligament Injuries (ACL). Most injuries to the ACL are non-contact rotational forces to the knee or the knee being put into a position of hyperextension. This may be an isolated injury or other structures such as the joint capsule, the menisci, or the MCL may also be injured. With injury to the ACL, the patient may state there was a “pop” or state “my knee gave out”. This injury is often accompanied by immediate onset of swelling in the knee and is often treated surgically depending on the level of performance of the patient. An injury to the ACL is more common in women than men due to specific anatomical differences. In order to test for injury to the ACL, and anterior drawer test and Lachman’s test can be completed in order to look for excess anterior displacement of the tibia on the femur. A pivot shift test is also used to determine if there is injury to the ACL. For post-surgical rehabilitation, open chain knee extension is contraindicated. Posterior Cruciate Ligament Injuries (PCL). The PCL is one of the strongest ligaments in the body. The most common mechanism of injury to the PCL is hitting the dashboard in a motor vehicle accident or falling on a bent knee, placing a posterior force on the tibia. This ligament can also be damaged as the result of a rotational force or hyperextension. Special tests used in order to test for injury to this joint include, posterior drawer test and the sag sign, looking for posterior displacement of the tibia on the femur. Depending on the severity of the injury, injury to the PCL may be treated surgically or nonsurgically. For post-surgical rehabilitation, open chain knee flexion is contraindicated. Medial and Lateral Meniscus Injuries. The outer ⅓ of the menisci is the only area of the menisci that has a good blood supply and a good potential to heal without surgery. The middle ⅓ of the menisci may have healing potential and the inner ⅓ of the menisci has no blood supply and will not heal, requiring surgical management. The most common mechanism of injury to the menisci is a forced rotation while flexing or extending the knee. Forced tibia external rotation usually results in injury to the medial meniscus, and forced tibial internal rotation usually results in injury to the lateral meniscus. With a meniscal injury, the patient may
  40. 40. Lower Extremity Arthrology   40   complain of a “locking” feeling in the knee and a slower onset of swelling. Four clinical features suggestive of a meniscal injury include: joint line tenderness, mild to moderate effusion that occurs over 1-2 days, positive McMurray’s, Apley’s, Thessaly’s test, or functional squat, and quadriceps atrophy over the first week or two following the injury. Patellofemoral Joint Overview The patellofemoral joint is between the articular side of the patella and the intercondylar groove of the femur. This joint is arthrodial (plane), non-axial, multiplanar. The movement of the joint is dictated by the trochlear groove. The patellofemoral joint slides superiorly when the knee extends and inferiorly when the knee flexes. A slight amount of medial and lateral deviation, as well as tilting, takes place during normal movement. The joint is stabilized by the forces produced by the quadriceps muscle, the fit of the joint surfaces, and passive restraint from the surrounding retinacular fibers and capsule. The patella is the largest sesamoid bone in the body. The patella is attached to the tibial tuberosity by the patellar tendon and is buried within the quadriceps tendon superiorly. Two facets exist on the posterior articular surface of the patella (Figure 21). The lateral facet is larger and slightly concave and it moves along the lateral condyle of the femur. The medial facet has different variations. It moves along the medial condyle of the femur. Most patellae also have an odd facet, which is a second vertical ridge between the medial border that separates the medial facet from an extreme medial edge. An important stabilizer of the patella is the vastus medialis obliquus muscle, which helps with the patella alignment. Neurovasculature. The circulatory blood supply to the patella is made up of branches of six main arteries: the descending genicular, the superior medial and lateral genicular, the inferior medial and lateral genicular, and the anterior genicular. These branches anastomose, forming the prepatellar arterial network and, Figure  21  Patellar  Anatomy
  41. 41. Lower Extremity Arthrology Guide 41   with the transverse infrapatellar artery, form the extraosseous patellar supply. Other smaller arteries originating from the popliteal and quadriceps arteries supply the patella entering at the base and the lateral sides. The infrapatellar branch of the saphenous nerve innervates the anterior aspect of the knee, which is a sensory nerve. Tissue Layers • Skin o Epidermis o Dermis o Hypodermis • Superficial fascia- fascia lata o Subcutaneous tissue • Deep fascia • Muscles and tendons o Quadriceps tendon • Arterial supply o Descending genicular artery o superior medial genicular artery o lateral genicular artery o Inferior medial genicular artery o Anterior genicular artery o Popliteal artery • Innervation o Saphenous nerve o Posterior tibial nerve o Obturator nerve o Femoral nerve • Ligaments o Patellar ligament • Fibrous joint capsule o Synovial membrane o Ligaments § Medial patellofemoral ligament § Lateral patellofemoral ligament § Medial patellar retinaculum § Lateral patellar retinaculum § Iliotibial tract o Bursa § prepatellar bursa § suprapatellar bursa § superficial infrapatellar bursa § deep infrapatellar bursa o Plicae § suprapatellar plica § infrapatellar plica § medial plica o Fat pads