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Hip Biomechanics SRS

The hip complex involves several joints and structures that allow movement in multiple planes. The hip joint itself is a ball and socket joint formed by the femoral head and acetabulum. Several angles describe the orientation of the femoral head and neck, including inclination, torsion, and anteversion/retroversion. Ligaments and the labrum provide stability to the joint while permitting movement. The close-packed position with extension and medial rotation maximizes joint congruency and stability.

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THE HIP COMPLEX BIOMECHANICS 1
Sreeraj S R HIP JOINT • Diarthrodial joint with 3 DoF. • Flexion/extension in sagittal plane • Abduction/adduction in frontal plane • Medial/lateral rotation in transverse plane • The primary function of the hip joint is to support the weight of the Head, Arms, and Trunk (HAT) both in static erect 2
Sreeraj S R PROXIMAL ARTICULAR SURFACE • The acetabulum (lunate surface) is formed by the union of the three bones of the pelvis, with only the upper horseshoe-shaped area being articular. • Full ossification of the pelvis occurs between 20 and 25 years of age. • The acetabulum is positioned laterally with an inferior and anterior tilt. 3 Levangie PK, Norkin CC. Joint structure and function : a comprehensive analysis. 5th ed. Philadelphia, Pa: F.A. Davis Company; 2011. p. 356–94.
Sreeraj S R ACETABULAR ANTEVERSION • Acetabular anteversion angle describes the extent to which the acetabulum surrounds the femoral head in the horizontal plane. • A value of 20 degrees is typical. • Excessive anteroversion may lead to anterior joint dislocation (especially during excessive external rotation). 4 Anterior edges Posterior edges Nick D, Jim N, Stefan K .Combined Acetabular and Femoral Version Angle in Normal Male and Female Populations From CT Data. The British Editorial Society of Bone & Joint Surgery. 2013 95(15): 168-168. doi: 10.1302/1358- 992X.95BSUPP_15.ISTA2012-168
Sreeraj S R ACETABULAR TILT ANGLE • Acetabular tilt is an index of rotational position of the acetabulum with reference to the anterior pelvic plane. • tilted 20° in sagittal plane. 5 Fujii M, Nakashima Y, Sato T, Akiyama M, Iwamoto Y. Acetabular tilt correlates with acetabular version and coverage in hip dysplasia. Clin Orthop Relat Res. 2012;470(10):2827–2835. doi:10.1007/s11999-012-2370-z ASIS pubic tubercles
Sreeraj S R ACETABULAR INCLINATION ANGLE • Defined as the angle between the supero inferior acetabular axis and the longitudinal axis in frontal plane. • 50° is typical. 6 Superior edge Inferior edge Murray DW. The definition and measurement of acetabular orientation. J Bone Joint Surg Br. 1993 Mar;75(2):228-32.
Sreeraj S R CENTRE EDGE ANGLE • Centre edge angle of Wiberg: 25 – 300 normal • <16°definite dysplasia • 16° to 25° possible dysplasia • >40° may indicate Coxa profunda 7 The CEA is formed between a vertical line through the center of the femoral head and a line connecting the center of the femoral head and the bony edge of the acetabulum. The acetabular labrum deepens the acetabulum. Levangie PK, Norkin CC. Joint structure and function : a comprehensive analysis. 5th ed. Philadelphia, Pa: F.A. Davis Company; 2011. p. 356–94.
Sreeraj S R ACETABULAR LABRUM 1. A fibrocartilaginous rim attached to the margin of the acetabular socket. 2. Deepens the acetabular socket. 3. With the transverse acetabular ligament it forms a complete circle. • Nerve endings within the labrum not only provide proprioceptive feedback but can also be a source of pain. 8
Sreeraj S R DISTAL ARTICULAR SURFACE • The articular area of the femoral head forms approximately two thirds of a sphere and is more circular than the acetabulum. • The femoral neck is angulated so that the femoral head faces medially, superiorly, and anteriorly with respect to the femoral shaft and distal femoral condyles. 9
Sreeraj S R ANGLE OF INCLINATION 10 • The axis of the femoral head and neck forms an angle with the axis of the femoral shaft called the angle of inclination. • The angle of inclination of the femur approximates 125° normally • With a normal angle of inclination, the greater trochanter lies at the level of the center of the femoral head. Coxa Valga Normal Coxa Vara
Sreeraj S R ANGLE OF INCLINATION 11 • Coxa valga leads to; •  bending force across femoral neck •  in lateral trabecular system •  Abductor force •  the contact of femoral articular surface with acetabulum.
Sreeraj S R ANGLE OF INCLINATION 12 • Coxa vara leads to; •  bending force along femoral neck. •  tensile stress on lateral trabecular system •  the predisposition toward femoral neck fracture. •  chance of slipped capital femoral epiphysis in adolescence
Sreeraj S R ANGLE OF TORSION 13
Sreeraj S R ANGLE OF TORSION • Anteversion: > 15-180 • Retroversion: < 15-180 14
Sreeraj S R ANTEVERSION In the supine position with the femoral condyles parallel to the supporting surface, the anteverted femoral head is exposed anteriorly. Lateral rotation will be limited, but medial rotation is relatively excessive. In standing, the anteverted femur tends to medially rotate within the acetabulum, resulting in medial rotation of the femoral condyles in relation to the plane of progression leading to medial femoral torsion. 15
Sreeraj S R ANTEVERSION • Reduces hip joint stability because the femoral articular surface is more exposed anteriorly. • Excessive femoral anteversion can cause instability, damage of the articular cartilage and acetabular labrum, and eventually osteoarthritis. • It can cause a decrease in the length of the abductor lever arm resulting in additional abductor muscle force requirement. • May cause increased hip and knee adduction moments, an intoeing gait and patellofemoral maltracking, with resultant knee pain and arthritis. 16
Sreeraj S R RETROVERSION • Femoral retroversion can cause damage to the labrum and articular cartilage, due to impingement between the femoral neck and acetabulum leading to osteoarthritis of the hip. • An increased risk of slipped capital femoral epiphysis • Susceptibility to a traumatic posterior hip dislocation. • Residual, untreated femoral retroversion may be a reason why hip preserving surgeries may fail, especially after the arthroscopic treatment of hip impingement. 17
Sreeraj S R COAPTATION OF THE ARTICULAR SURFACES • In the neutral or standing position, the articular surface of the femoral head remains exposed anteriorly and somewhat superiorly. • Not a true physiological position of the hip joint. (Kapandji) • Maximum articular contact of the head of the femur with the acetabulum is obtained when the femur 18 Levangie PK, Norkin CC
Sreeraj S R COAPTATION OF THE ARTICULAR SURFACES • The stability of the hip joint is assisted by gravity, in the straight position by opposing forces (ascending white arrow) opposite to the body weight (descending white arrow). • The acetabular labrum, widens and deepens the acetabulum (black arrows), setting the stage for a fibrous interlocking and retaining system. • The labrum retains the femoral head with the help of the zona orbicularis of the fibrous capsule , which holds the femoral neck 19 https://en.wikipedia.org/wiki/Zona_orbicul Kapandji AI
Sreeraj S R COAPTATION OF THE ARTICULAR SURFACES • Atmospheric pressure plays an important part in securing the articular coaptation of the hip joint. • The acetabular fossa may be important in setting up a partial vacuum in the joint so that atmospheric pressure contributes to stability by helping maintain contact between the femoral head and the acetabulum. 20 Kapandji AI acetabular fossa
Sreeraj S R COAPTATION OF THE ARTICULAR SURFACES • The periarticular ligaments and muscles are vital in maintaining the coaptation of the articular surfaces. • Their functions are reciprocally balanced. (Figure horizontal section) • Thus anteriorly the muscles are very few (blue arrow) and the ligaments (black arrows) are strong, while posteriorly the muscles (red arrow) predominate. • This coordinated activity keeps the femoral head (green arrow) closely applied to the 21 Kapandji AI
Sreeraj S R COAPTATION OF THE ARTICULAR SURFACES • Tensed ligaments in extension are efficient in securing coaptation. • In flexion the ligaments are slack, and the opposite happens. • This mechanism can be easily understood using the mechanical model, where a. parallel strings run between two wooden circles b. When one circle is rotated relative to the other, they are brought closer together. 22Kapandji AI extension flexion
Sreeraj S R COAPTATION OF THE ARTICULAR SURFACES • The position of flexion is a position of instability for the hip joint because of the slackness of the ligaments. • Flexion with adduction as in legs crossed position is easy to cause a posterior dislocation of the hip joint on a femoral impact. • Dashboard injury 23 Kapandji AI
Sreeraj S R THE ARTICULAR CAPSULE • The capsule is attached proximally to the entire periphery of the acetabulum beyond the acetabular labrum. • Fibers near the proximal attachment forms a tight ring just below the femoral head known as the zona orbicularis. 24
Sreeraj S R THE ARTICULAR CAPSULE • It is like a cylindrical sleeve helps to unite the articular surfaces • Made up of four types of fibres: 1. Longitudinal fibres, run parallel to the axis of the cylinder 2. Oblique fibres, spiral around the cylinder 3. Arcuate fibres, attached to the hip bone and forming an arc whose apex lies towards the middle of the sleeve. 4. Circular fibres, which are particularly abundant in the middle of the capsule and form the zona orbicularis (Weber's 25 Kapandji AI
Sreeraj S R THE LIGAMENTS • The hip joint is reinforced by four ligaments, of which three are extracapsular and one intracapsular. • The extracapsular ligamen ts are the iliofemoral, pubofemoral, and ischiofemoral ligaments. • The intracapsular ligament , the ligamentum teres, is attached to the acetabular 26 https://en.wikipedia.org/wiki/Hip#Ligaments
Sreeraj S R THE LIGAMENTS 27 “Y” ligament of Bigelow.
Sreeraj S R THE LIGAMENTS • During the change from the quadruped to the biped erect posture the pelvis moved into a position of extension relative to the femur • This made all the ligaments coiled around the femoral neck in the same direction. • Thus extension winds the ligaments around the neck more, tightening them, 28
Sreeraj S R ROLE OF THE LIGAMENTS IN EXTENSION • During hip extension: • all the ligaments become taut especially the inferior band of the iliofemoral ligament. • Thus responsible for checking the posterior tilt of the pelvis. 29 Example: the iliac bone rotates backwards while the femur sta
Sreeraj S R ROLE OF THE LIGAMENTS IN FLEXION • During hip flexion: • All the ligaments are relaxed • This relaxation of the ligaments is one of the factors responsible for the instability of the hip in this position. 30 Example: the iliac bone tilts forward while the femur stays
Sreeraj S R ROLE OF THE LIGAMENTS IN LATERAL ROTATION • During lateral rotation of the hip: • all the anterior ligaments running horizontally, i.e. the superior band of the iliofemoral and pubofemoral are taut. • and slackening of the ischio femoral ligament 31
Sreeraj S R ROLE OF THE LIGAMENTS IN MEDIAL ROTATION • During medial rotation: • all the anterior ligaments running horizontally are slackened, • while the ischiofemoral ligament becomes taut • The vertical inferior band of the iliofemoral ligament limits medial rotation, when the hip is in extension. 32
Sreeraj S R ROLE OF THE LIGAMENTS IN ADDUCTION • The superior band is tightened considerably, • the inferior band only slightly, • pubofemoral ligament relaxes. • The ischiofemoral ligament is stretched during adduction 33 Ischiofemoral
Sreeraj S R ROLE OF THE LIGAMENTS IN ABDUCTION • The pubofemoral ligament is tightened considerably • The superior and the inferior bands are relaxed. • The ischiofemoral ligament tenses up during abduction. 34 Ischiofemoral
Sreeraj S R ROLE OF THE LIGAMENTUM TERES • A strong intrinsic stabilizer that resists joint subluxation forces. • It is most taut when the hip is in its least stable positions i.e. flexion, adduction, and external rotation. • Adduction is the only position where the ligament is really under tension. • And is lax in hip abduction and internal rotation. 35 Cerezal L, Kassarjian A, Canga A, et al. Anatomy, Biomechanics, Imaging, and Management of Ligamentum Teres Injuries. RadioGraphics. 2010;30(6):1637-1651. doi:10.1148/rg.306105516
Sreeraj S R CAPSULOLIGAMENTOUS TENSION • Hip joint extension, with slight abduction and medial rotation, is the close-packed position for the hip joint. • The capsuloligamentous tension at the hip joint is least when the hip is in moderate flexion, slight abduction, and midrotation. • In this position, the normal intra-articular pressure is minimized, and the capacity of the synovial capsule to accommodate abnormal amounts of fluid is greatest. • This is the position assumed by the hip when there is pain arising from capsuloligamentous problems or from excessive intra-articular pressure caused by extra fluid (blood or synovial fluid) in the joint. 36
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING - FEMUR • The trabeculae are calcified plates of tissue within the cancellous bone as a result of interaction between mechanical stresses and structural adaptation created by the transmission of forces between bones. • The trabeculae line up along lines of stress and form systems that normally adapt to stress requirements. 37
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING - FEMUR • The HAT loads the head of the femur, • The GRF comes up the shaft of the femur, • resulting in a moment arm (MA) • This bending moment creates tensile stress on the superior aspect of the femoral neck and compressive stress on the inferior aspect. 38
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING - FEMUR • A complex set of adaptive forces prevents the rotation and resists the shear forces that the force couple causes; • These forces are the structural resistance of two major and three minor trabecular systems • Two major are the medial compressive and lateral tensile trabecular systems. 39
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING - FEMUR • The zone of weakness is an area in the femoral neck in which the trabeculae are relatively thin and do not cross each other. • The zone of weakness of the femoral neck is particularly susceptible to the bending forces across the area and can fracture as it has less reinforcement and thus more potential for failure. 40
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING - FEMUR • Changes in trabecular patterns due to altered angle. • Coxa valga leads to more compression trabeculae, coxa vara to more tension trabeculae. 41
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING - FEMUR • The forces of HAT and the ground reaction force also act on the femoral shaft. • As the shaft of the femur lies at an angle instead of vertical, • loading on the oblique femur results in bending stresses in the shaft. • The medial cortical bone of the femoral shaft (diaphysis) must resist compressive stresses, whereas the lateral cortical bone must resist tensile stresses 42
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING - ACETABULUM • The primary weight- bearing surface of the acetabulum, or dome of the acetabulum, is located on the superior portion of the lunate surface. • In the normal hip, the dome lies directly over the center of rotation of the femoral head. • Peak contact pressures during unilateral stance to be located near the dome. 43
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING - ACETABULUM • Normal stress distribution can be altered; • with a lack of femoral head coverage by the acetabulum due to decreased center edge angle • Excessive acetabular anteversion 44 Coxa Valga Normal Coxa Vara
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING – ARTICULAR CARTILAGE • The superior femoral head receives compression from • the dome in standing • from the posterior acetabulum in sitting and • the anterior acetabulum in extension. • Full loading of the hip joint ensures congruence and load distribution between the larger femoral head and the 45
Sreeraj S R STRUCTURAL ADAPTATIONS TO WEIGHT BEARING – ARTICULAR CARTILAGE • Persisting incongruence of the acetabulum could result in; • incomplete compression of the dome cartilage and, • inadequate fluid exchange to maintain cartilage nutrition. • The articular cartilage is avascular, so it dependent on compression & release forces to move nutrients through the tissue; • Both too little compression and excessive compression can lead to compromise of the cartilage structure. 46
Sreeraj S R MOTION OF THE FEMUR ON THE ACETABULUM • The motions of the hip joint are the movement of the convex femoral head within the concavity of the acetabulum as the femur moves through its three degrees of freedom: 1. flexion/extension, 2. abduction/adduction, and 3. medial/lateral rotation. • The femoral head will glide within the acetabulum in a direction opposite to motion of the distal end of the femur. 47
Sreeraj S R MOTION OF THE FEMUR ON THE ACETABULUM • Flexion and extension of the femur occur as an almost pure spin of the femoral head around a coronal axis. • However, flexion and extension from other positions (e.g., in abduction or medial rotation) must include both spinning and gliding of the articular surfaces, depending on the combination of motions. • The motions of abduction/adduction and medial/lateral rotation must include both spinning and gliding of the femoral head within the acetabulum • The intra-articular motion occurs in a direction opposite to motion of the distal end of the femur. • For Example, The head spins posteriorly in flexion and48
Sreeraj S R MOTION OF THE FEMUR ON THE ACETABULUM • Flexion of the hip is generally about 120° with the knee flexed. • It is limited to 90° with the knee extended due to passive tension in the two joint hamstrings muscle group • Hip extension is considered to have a range of 10 ° to 30°. • When hip extension is combined with knee flexion, passive tension in the two-joint rectus femoris muscle may limit the movement. 49
Sreeraj S R MOTION OF THE FEMUR ON THE ACETABULUM • The femur can be abducted 45° to 50° and adducted 20° to 30°. • Abduction can be limited by the two-joint Gracilis muscle • Adduction limited by the Tensor Fascia Lata (TFL) muscle and its associated Iliotibial (IT) band. • Medial and lateral rotation of the hip are usually measured with the hip joint in 90° of flexion; the typical range is 42° to 50°. • Femoral anteversion is correlated with decreased range of lateral rotation and increased range of medial rotation. 50
Sreeraj S R MOTION OF THE FEMUR ON THE ACETABULUM • Normal gait on level ground requires at least the • following hip joint ranges: • 30° flexion, • 10° extension, • 5° of both abduction and adduction, and • 5° of both medial and lateral rotation. • Walking on uneven terrain or stairs increase the need for joint range. 51
Sreeraj S R MOTION OF THE PELVIS ON THE FEMUR • The motion of the pelvis are the same three degrees of freedom for the hip joint are accomplished by the pelvis rather than by the femur. • Anterior and posterior pelvic tilts are motions of the entire pelvic ring in the sagittal plane around a coronal axis. 52 A. The pelvis in its normal position in erect stance. B. Posterior tilting of the pelvis moves the symphysis pubis superiorly on the fixed femur. The hip joint extends. C. In anterior tilting, the anterior superior iliac spines move inferiorly on the fixed femur. The hip joint flexes.
Sreeraj S R MOTION OF THE PELVIS ON THE FEMUR • Lateral pelvic tilt is a frontal plane motion of the entire pelvis around an anteroposterior axis. • In the normally aligned pelvis, a line through the anterior superior iliac spines is horizontal. A. Hiking of the pelvis around the right hip joint results in right hip abduction. B. Dropping of the pelvis around the right hip joint 53
Sreeraj S R MOTION OF THE PELVIS ON THE FEMUR • Lateral Shift of the Pelvis can also occur in bilateral stance. • When the pelvis is shifted to the right in bilateral stance, the right hip joint adducted, and the left hip joint abducted. • To return to neutral position in same stance the right abductor and left adductor muscles work synergistically to shift the 54
Sreeraj S R MOTION OF THE PELVIS ON THE FEMUR • Pelvic Rotation is motion of the entire pelvic ring in the transverse plane around a vertical axis. • Rotation can occur both in bilateral stance as well as in single-limb support around the axis of the weight-bearing hip joint. 55 A. Forward rotation of the pelvis around the left hip joint results in medial rotation of the left hip joint. B. Neutral position of the pelvis and the left hip joint. C. Backward rotation of the pelvis around the left hip joint results in lateral rotation of the left hip joint.
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Sreeraj S R COORDINATED MOTIONS OF THE FEMUR, PELVIS, AND LUMBAR SPINE • When the pelvis moves on a relatively fixed femur, there are two possible outcomes to consider. 1. Either the head and trunk will follow the motion of the pelvis (moving the head through space) open chain responses or 2. The head will continue to remain relatively upright and vertical despite the pelvic motions, closed chain responses. 57
Sreeraj S R COORDINATED MOTIONS OF THE FEMUR, PELVIS, AND LUMBAR SPINE • Pelvifemoral Motion is a coordinated movement of femur, pelvis, and spine to produce a larger ROM than is available to one segment alone. • The lower, caudal end of the axial skeleton is firmly attached to the pelvis by way of the sacroiliac joints. Therefore, rotation of the pelvis over the femoral heads typically changes the configuration of the lumbar spine. This important kinematic relationship is known as lumbopelvic rhythm • Predominantly an open-chain motion but not exclusive. • AIanalogous to scapulohumeral motion. 58
Sreeraj S R COORDINATED MOTIONS OF THE FEMUR, PELVIS, AND LUMBAR SPINE 59
Sreeraj S R COORDINATED MOTIONS OF THE FEMUR, PELVIS, AND LUMBAR SPINE • Closed-Chain Hip Joint Function is formed because both ends of the chain (both feet in this example) are “fixed” and movement at any one joint in the chain invariably involves movement at one or more other links in the chain. 60
Sreeraj S R COORDINATED MOTIONS OF THE FEMUR, PELVIS, AND LUMBAR SPINE PELVIC MOTION HIP JOINT MOTION LUMBAR SPINE MOTION Anterior pelvic tilt Hip flexion Lumbar extension Posterior pelvic tilt Hip extension Lumbar flexion Lateral pelvic tilt (pelvic drop) Right hip adduction Right lateral flexion Lateral pelvic tilt (pelvic hike) Right hip abduction Left lateral flexion Forward rotation Right hip medial rotation Rotation to the left (in closed chain) Backward rotation Right hip lateral rotation Rotation to the right (in closed chain) 61
Sreeraj S R MUSCLES OF THE HIP • The line of pull of a muscle is the long axis of the muscle. • The angle of pull is the angle between the long axis of the bone (lever arm) and the line of pull of the muscle. • The angle of pull and moment arm of the muscle both change as the joint goes through its range of motion. 62 A lateral view shows the sagittal plane line of force of several hip muscles.
Sreeraj S R MUSCLES OF THE HIP • A muscle action describes the potential direction of rotation of the joint following its activation • A muscle torque describes the “strength” of the action. • A muscle torque can be estimated by the product of the muscle force (in Newtons) and the muscle’s associated moment arm length (meters). 63
Sreeraj S R HIP FLEXORS • Primary 1. Iliopsoas 2. Rectus femoris 3. Sartorius 4. Tensor fasciae latae 5. Pectineus • Secondary 1. Adductor brevis 2. Gracilis 3. Gluteus minimus (anterior fibers) 64
Sreeraj S R HIP FLEXORS 65
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Sreeraj S R PELVIC-ON-FEMORAL HIP FLEXION • The anterior pelvic tilt is performed by a force-couple between the hip flexors and low-back extensor muscles. • Any muscle capable of hip flexion is equally capable of tilting the pelvis anteriorly. • Also note a consequent increase in lordosis at the lumbar spine. • Greater lordosis increases the compressive loads on the lumbar apophyseal joints and shear force at the lumbosacral junction. 70
Sreeraj S R FEMORAL-ON-PELVIC HIP FLEXION • Open chain action. • The synergistic action of one representative abdominal muscle (rectus abdominis) in SLR. A. With normal activation of the abdominal muscles, the pelvis is stabilized and prevented from anterior tilting by the downward pull of the hip flexor muscles. B. With reduced activation of the abdominal muscles, contraction of the hip flexor muscles is shown producing a 71
Sreeraj S R HIP ADDUCTORS • Primary 1. Pectineus 2. Adductor longus 3. Gracilis 4. Adductor brevis 5. Adductor magnus • Secondary 1. Biceps femoris (long head) 2. Gluteus maximus (lower fibers) 3. Quadratus femoris 72
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Sreeraj S R HIP ADDUCTORS 78 The anatomic organization and proximal attachments of the adductor muscle group.
Sreeraj S R FRONTAL PLANE FUNCTION IN HIP ADDUCTION • The bilateral cooperative action of selected adductor muscles. • Example: kicking a soccer ball. • The left adductor magnus is shown actively producing pelvic - on - femoral adduction. • Several right adductor muscles are shown actively producing femoral - on - pelvic adduction 79 There is concentric activation of the left adductor muscles and eccentric activation of the left gluteus medius to decelerate and control the motions.
Sreeraj S R SAGITTAL PLANE FUNCTION IN HIP ADDUCTION • Adductor muscles are considered flexors from the extended position. • When outside the 400 to 700 flexed position, the individual adductor muscles regain leverage as significant extensors of the hip. • From a hip position of near extension, the line of force of the adductor longus is well anterior to the medial-lateral axis of rotation. • The adductor longus now has a flexor moment arm and 80 These contrasting actions are based on the change in line of force of the adductor longus, relative to the medio lateral axis of rotation at the hip.
Sreeraj S R HIP INTERNAL ROTATORS • Primary Not applicable • no muscle with any potential to internally rotate the hip lies even close to the horizontal plane. From the anatomic position, therefore, it is difficult to assign any muscle as a primary internal rotator of the hip. • Secondary 1. Gluteus minimus (anterior fibers) 2. Gluteus medius (anterior fibers) 3. Tensor fasciae latae 4. Adductor longus 5. Adductor brevis 6. Pectineus 7. Piriformis 81
Sreeraj S R HIP INTERNAL ROTATORS • A superior view depicts the horizontal plane line of force of several muscles that cross the hip. • The external rotators are indicated by solid lines and • the internal rotators by dashed lines. 82
Sreeraj S R HIP INTERNAL ROTATORS • The adductor muscles as secondary internal rotators of the hip. A. Because of the anterior bowing of the femoral shaft, a large segment of the linea aspera runs anterior to the longitudinal axis of rotation. B. A superior view of the right hip shows the horizontal line of force of the adductor longus causes an internal rotation torque by producing a force that passes anterior to the axis of rotation 83
Sreeraj S R HIP EXTENSORS • Primary 1. Gluteus maximus 2. Biceps femoris (long head) 3. Semitendinosus 4. Semimembranosus 5. Adductor magnus (posterior head) • Secondary 1. Gluteus medius (posterior fibers) 2. Adductor magnus (anterior head) 84 With the hip flexed to at least about 70 degrees and beyond, most adductors muscles except pectineus can assist with hip extension.
Sreeraj S R HIP EXTENSORS 85
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Sreeraj S R PELVIC-ON-FEMORAL HIP EXTENSION PERFORMING A POSTERIOR PELVIC TILT • The force couple between representative hip extensors and abdominal muscles used to posteriorly tilt the pelvis. • Note the decreased lordosis at the lumbar spine. • The extension at the hip stretches the iliofemoral ligament. 88
Sreeraj S R PELVIC-ON-FEMORAL HIP EXTENSION CONTROLLING A FORWARD LEAN OF THE BODY 89 A. Slight forward lean of the upper body displaces the body weight force slightly anterior to the medial- lateral axis of rotation at the hip. • This slightly flexed posture is restrained by minimal activation from the gluteus maximus and hamstring muscles.
Sreeraj S R PELVIC-ON-FEMORAL HIP EXTENSION CONTROLLING A FORWARD LEAN OF THE BODY 90 B. A more significant forward lean displaces the body weight force even farther anteriorly. • The greater flexion of the hips rotates the ischial tuberosities posteriorly, thereby increasing the hip extension moment arm of the hamstrings. • The gluteus maximus, however, remains relatively inactive in this position • The taut line (with arrowhead within the stretched hamstring muscles) indicates the increased passive tension.
Sreeraj S R FEMORAL-ON-PELVIC HIP EXTENSION • Consider the example of climbing a steep hill carrying a heavy pack. • The flexed position favours greater extension torque generation from the hip extensor muscles and many of the adductor muscles. • The flexed position of the right hip also imposes a large external (flexion) torque at the hip. 91 Activation is also required in low-back extensor muscles to stabilize the position of the pelvis.
Sreeraj S R HIP ABDUCTORS • Primary 1. Gluteus medius 2. Gluteus minimus 3. Tensor fasciae latae • Secondary 1. Piriformis 2. Sartorius 92
Sreeraj S R HIP ABDUCTORS 93
Sreeraj S R HIP ABDUCTORS 94
Sreeraj S R HIP ABDUCTORS 95
Sreeraj S R HIP ABDUCTORS • The gluteus medius and minimum have been likened to the “rotator cuff” of the hip, with the supraspinatus and subscapularis, respectively. • Also analogous to the deltoid muscle of the glenohumeral joint. • the anterior fibers of the gluteus medius are active in hip flexion and • the posterior fibers function during extension. • In the neutral hip, • the posterior portion of the medius will produce a lateral rotational moment and • the middle and anterior portions have small medial96
Sreeraj S R HIP ABDUCTOR MECHANISM: CONTROL OF FRONTAL PLANE STABILITY OF THE PELVIS DURING WALKING • During the stance phase the hip abductor muscles have a role in controlling the pelvis in the frontal plane and the horizontal plane. • During the single-limb support phase of gait the opposite leg is off the ground and swinging forward. • Without adequate abduction torque on the stance limb, the pelvis and trunk may drop uncontrollably toward the side of the swinging limb. 97
Sreeraj S R HIP ABDUCTOR MECHANISM: ROLE IN THE PRODUCTION OF COMPRESSION FORCE AT THE HIP • The counterclockwise torque (solid circle) is the product of the right hip abductor force (HAF) times internal moment arm (D) • The clockwise torque (dashed circle) is the product of body weight (BW) times external moment arm (D1). • Because the system is assumed to be in equilibrium, the torques in the frontal plane are equal in magnitude and opposite in direction: • HAF × D = BW × D1. 98 The illustration assumes that the pelvis and trunk are in static (linear and rotary) equilibrium about the right hip.
Sreeraj S R HIP ABDUCTOR MECHANISM: ROLE IN THE PRODUCTION OF COMPRESSION FORCE AT THE HIP • Note that the internal moment arm (D) used by the hip abductor muscles is about half the length of the external moment arm (D1) used by body weight. • So, hip abductor muscles must produce a force twice that of body weight in order to achieve stability during single-limb support. • This downward force is counteracted by a joint reaction force (JRF) of equal magnitude oriented in nearly the opposite direction. • The JRF angulation is strongly 99
Sreeraj S R HIP EXTERNAL ROTATORS • Primary 1. Gluteus maximus 2. Piriformis 3. Obturator internus 4. Gemellus superior 5. Gemellus inferior 6. Quadratus femoris • Secondary 1. Gluteus medius (posterior fibers) 2. Gluteus minimus (posterior fibers) 3. Obturator externus 4. Sartorius 5. Biceps femoris (long head) 100
Sreeraj S R HIP EXTERNAL ROTATORS 101
Sreeraj S R HIP EXTERNAL ROTATORS 102
Sreeraj S R PELVIC-ON-FEMORAL HIP EXTERNAL ROTATORS • With the right lower extremity firmly in contact with the ground, contraction of the right external rotators accelerates the anterior side of the pelvis and attached trunk to the left - contralateral to the fixed femur. • This action of planting a foot and “cutting” to the opposite side is the natural way to abruptly 103
Sreeraj S R HIP ROTATORS • The piriformis, reportedly an external rotator in full extension but an internal rotator at 90° or more of flexion. • Restrictions in the extensibility of this muscle are typically described as limiting passive hip internal rotation, and possibly compressing the underlying sciatic nerve. • A traditional method for stretching a tight piriformis is to combine full flexion and external rotation of the hip, typically performed with the knee flexed. 104
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE BILATERAL STANCE • In erect bilateral stance, • both hips are in neutral and • weight is evenly distributed between both legs. • The line of gravity falls just posterior to the axis for flexion/extension of the hip joint. • The posterior location of the line of gravity creates an extension moment of force around the hip which is largely checked by passive tension in the hip joint capsuloligamentous structures and activity of hip flexors. • In the frontal plane, the body weight is transmitted through the sacroiliac joints and pelvis to the right and left femoral heads. 105
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE BILATERAL STANCE • DR & DL : the gravitational moment arms • WR & WL : body weight • Because WR = WL • Magnitude of gravitational torque around hip is: WR X DR = WL X DL • Total hip joint compression = 4/6 X body weight 106
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE BILATERAL STANCE • In normal B/L stance, assuming no muscular forces maintain either sagittal or frontal plane stability at the hip joint, • the compression across each hip joint should be half the superimposed body weight • or one third of HAT to each hip. • Example: Assuming a body weight of 84 Kg. • The weight of HAT is 4/6 body weight. • 84 X 4/6 = 56 Kg. • Each hip receives 56/2 = 28 Kg. HAT: Head Arm Trunk 107
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE UNILATERAL STANCE • Full superimposed body weight (HAT) is being supported by the right hip joint. • The weight of the non- weight bearing left limb must now be supported along with the weight of HAT. • The magnitude of body weight (W) compressing the right hip joint is [4/6 X W] + [1/6 X W] 108
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE UNILATERAL STANCE Example: Assuming a body weight of 84 Kg. • The magnitude of body weight (W) compressing the right hip joint is [4/6 X W] + [1/6 X W] • 4/6 X 84 + 1/6 X 84 • 56 + 14 = 70 • So right hip joint compression body weight is 70 Kg • Now the hip joint in unilateral stance being compressed by body weight (gravity) concomitantly creating a torque around the hip joint. 109
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE UNILATERAL STANCE • The force of gravity acting on HAT and the non weight bearing left lower limb (HATLL) will create an adduction torque around the weight-bearing hip joint ( drop of non weight bearing limb) and an abduction counter torque by the hip abductor musculature. • The result will be joint compression or a joint reaction force that is a combination of both body weight and abductor muscular compression. 110
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE UNILATERAL STANCE Example: Assuming a body weight of 84 Kg. • So right hip joint compression body weight is 70 Kg • Add./LOG MA is 10 cm = 0.1m • Abd. MA is 5 cm = 0.05 m • HATLL torque add. = 70 X 0.1 = 7 Kg • So torque abd. = Torque Add./ Abd. MA = 7/0.05 = 140 Kg • The total hip joint compression, or joint reaction 111
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE COMPENSATORY LATERAL LEAN OF THE TRUNK • When the trunk is laterally flexed toward the stance limb, the moment arm of HATLL is substantially reduced. • The compensatory lateral lean of the trunk toward the painful stance limb will swing the line of gravity closer to the hip joint, thereby reducing the gravitational moment arm 112
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE COMPENSATORY LATERAL LEAN OF THE TRUNK Example: Assuming a body weight of 84 Kg. • So right hip joint compression body weight is 70 Kg • Add./LOG MA is 2.5 cm = 0.025m • Abd. MA is 5 cm = 0.05 m • HATLL torque add. = 70 X 0.025 = 1.75 Kg • So torque abd. = Torque Add./ Abd. MA = 1.75/0.05 = 35 Kg • The total hip joint compression, or joint reaction force is abd. torque + HATLL 113
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE USE OF A CANE IPSILATERALLY • Pushing downward on a cane held in the hand on the side of pain or weakness should reduce the superimposed body weight by the amount of downward thrust; • that is, some of the weight of HATLL would follow the arm to the cane, rather than arriving on the sacrum and the weight-bearing hip joint. • The proportion of body weight that passes through the cane will not pass through the hip joint and will not create an adduction torque around the supporting hip joint. 114
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE USE OF A CANE IPSILATERALLY Example: Assuming a body weight of 84 Kg. • If 84 kg push down on the kane with 15% BW = 84 X 0.15 = 12.6 will pass through kane • So the magnitude of HATLL is 70 – 12.6 = 57.4 • So right hip joint compression body weight is 57.4 Kg • Add./LOG MA is 10 cm = 0.1m • Abd. MA is 5 cm = 0.05 m • HATLL torque add. = 57.4 X 0.1 = 5.74 Kg • So torque abd. = Torque Add./ Abd. MA = 5.74/0.05 = 114 Kg • The total hip joint compression, or joint reaction force is abd. torque + HATLL W • i.e. 114 + 57.4 = 172.2 Kg 115
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE USE OF A CANE CONTRALATERALLY • When a cane is placed in the hand opposite the painful supporting hip, the weight passing through the right hip is reduced. • Activation of the left latissimus dorsi provides a counter torque to that of HATLL and diminishes the need for a contraction of the right hip abductors. • In this example the MA of the cane is estimated to 116
Sreeraj S R HIP JOINT FORCES AND MUSCLE FUNCTION IN STANCE USE OF A CANE CONTRALATERALLY Example: Assuming a body weight of 84 Kg. • If 84 kg push down on the kane with 15% BW = 84 X 0.15 = 12.6 will pass through kane • So the magnitude of HATLL is 70 – 12.6 = 57.4 • So right hip joint compression body weight is 57.4 Kg • Adduction/LOG MA is 10 cm = 0.1m • Abduction MA is 50 cm = 0.5 m • HATLL torque add. = 57.4 X 0.1 = 5.74 Kg • Cane torque = 12.6 X 0.5 = 6.3 • If assume that the gravitational adduction torque and the counter torque provided by the cane offset each other there would be no need for hip abductor muscle force • The total hip joint compression, or joint reaction force is abd. torque + HATLL W 117
Sreeraj S R • https://hipandkneebook.c om/biomechanics 118
Sreeraj S R REFERENCES 1. Martin RL, Kivlan B. The Hip Complex. In: Levangie PK, Norkin CC, editors. Joint structure and function : a comprehensive analysis. 5th ed. Philadelphia, Pa: F.A. Davis Company; 2011. p. 356–94. 2. Kapandji AI. The Hip. In: Physiology of the Joints: Volume 2 Lower Limb. 6th ed. Edinburgh ; New York: Churchill Livingstone/Elsevier; 2011. p. 2–65. 3. Uritani D, Fukumoto T. Differences of Isometric Internal and External Hip Rotation Torques among Three Different Hip Flexion Positions. Journal of Physical Therapy Science. 2012;24(9):863-865. doi:10.1589/jpts.24.863 4. Neumann DA. Kinesiology of the Hip: A Focus on Muscular Actions. Journal of Orthopaedic & Sports Physical Therapy. 2010 Feb;40(2):82–94. 5. Therapeutic Exercise for Musculoskeletal Injuries [Internet]. [cited 2020 Feb 4]. Available from: https://humankinetics.com/AcuCustom/Sitename/DAM/153/Houglum_78-79.pdf 6. Lippert L. Chapter 17 Hip. In: Clinical kinesiology and anatomy. 4th ed. Philadelphia: F.A. Davis Company; 2006. p. 233–49. 119

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Hip Biomechanics SRS

  • 1.
    THE HIP COMPLEXBIOMECHANICS 1
  • 2.
    Sreeraj S R HIP JOINT •Diarthrodial joint with 3 DoF. • Flexion/extension in sagittal plane • Abduction/adduction in frontal plane • Medial/lateral rotation in transverse plane • The primary function of the hip joint is to support the weight of the Head, Arms, and Trunk (HAT) both in static erect 2
  • 3.
    Sreeraj S R PROXIMAL ARTICULARSURFACE • The acetabulum (lunate surface) is formed by the union of the three bones of the pelvis, with only the upper horseshoe-shaped area being articular. • Full ossification of the pelvis occurs between 20 and 25 years of age. • The acetabulum is positioned laterally with an inferior and anterior tilt. 3 Levangie PK, Norkin CC. Joint structure and function : a comprehensive analysis. 5th ed. Philadelphia, Pa: F.A. Davis Company; 2011. p. 356–94.
  • 4.
    Sreeraj S R ACETABULAR ANTEVERSION •Acetabular anteversion angle describes the extent to which the acetabulum surrounds the femoral head in the horizontal plane. • A value of 20 degrees is typical. • Excessive anteroversion may lead to anterior joint dislocation (especially during excessive external rotation). 4 Anterior edges Posterior edges Nick D, Jim N, Stefan K .Combined Acetabular and Femoral Version Angle in Normal Male and Female Populations From CT Data. The British Editorial Society of Bone & Joint Surgery. 2013 95(15): 168-168. doi: 10.1302/1358- 992X.95BSUPP_15.ISTA2012-168
  • 5.
    Sreeraj S R ACETABULAR TILTANGLE • Acetabular tilt is an index of rotational position of the acetabulum with reference to the anterior pelvic plane. • tilted 20° in sagittal plane. 5 Fujii M, Nakashima Y, Sato T, Akiyama M, Iwamoto Y. Acetabular tilt correlates with acetabular version and coverage in hip dysplasia. Clin Orthop Relat Res. 2012;470(10):2827–2835. doi:10.1007/s11999-012-2370-z ASIS pubic tubercles
  • 6.
    Sreeraj S R ACETABULAR INCLINATIONANGLE • Defined as the angle between the supero inferior acetabular axis and the longitudinal axis in frontal plane. • 50° is typical. 6 Superior edge Inferior edge Murray DW. The definition and measurement of acetabular orientation. J Bone Joint Surg Br. 1993 Mar;75(2):228-32.
  • 7.
    Sreeraj S R CENTRE EDGEANGLE • Centre edge angle of Wiberg: 25 – 300 normal • <16°definite dysplasia • 16° to 25° possible dysplasia • >40° may indicate Coxa profunda 7 The CEA is formed between a vertical line through the center of the femoral head and a line connecting the center of the femoral head and the bony edge of the acetabulum. The acetabular labrum deepens the acetabulum. Levangie PK, Norkin CC. Joint structure and function : a comprehensive analysis. 5th ed. Philadelphia, Pa: F.A. Davis Company; 2011. p. 356–94.
  • 8.
    Sreeraj S R ACETABULAR LABRUM 1.A fibrocartilaginous rim attached to the margin of the acetabular socket. 2. Deepens the acetabular socket. 3. With the transverse acetabular ligament it forms a complete circle. • Nerve endings within the labrum not only provide proprioceptive feedback but can also be a source of pain. 8
  • 9.
    Sreeraj S R DISTAL ARTICULARSURFACE • The articular area of the femoral head forms approximately two thirds of a sphere and is more circular than the acetabulum. • The femoral neck is angulated so that the femoral head faces medially, superiorly, and anteriorly with respect to the femoral shaft and distal femoral condyles. 9
  • 10.
    Sreeraj S R ANGLE OFINCLINATION 10 • The axis of the femoral head and neck forms an angle with the axis of the femoral shaft called the angle of inclination. • The angle of inclination of the femur approximates 125° normally • With a normal angle of inclination, the greater trochanter lies at the level of the center of the femoral head. Coxa Valga Normal Coxa Vara
  • 11.
    Sreeraj S R ANGLE OFINCLINATION 11 • Coxa valga leads to; •  bending force across femoral neck •  in lateral trabecular system •  Abductor force •  the contact of femoral articular surface with acetabulum.
  • 12.
    Sreeraj S R ANGLE OFINCLINATION 12 • Coxa vara leads to; •  bending force along femoral neck. •  tensile stress on lateral trabecular system •  the predisposition toward femoral neck fracture. •  chance of slipped capital femoral epiphysis in adolescence
  • 13.
  • 14.
    Sreeraj S R ANGLE OFTORSION • Anteversion: > 15-180 • Retroversion: < 15-180 14
  • 15.
    Sreeraj S R ANTEVERSION In thesupine position with the femoral condyles parallel to the supporting surface, the anteverted femoral head is exposed anteriorly. Lateral rotation will be limited, but medial rotation is relatively excessive. In standing, the anteverted femur tends to medially rotate within the acetabulum, resulting in medial rotation of the femoral condyles in relation to the plane of progression leading to medial femoral torsion. 15
  • 16.
    Sreeraj S R ANTEVERSION • Reduceship joint stability because the femoral articular surface is more exposed anteriorly. • Excessive femoral anteversion can cause instability, damage of the articular cartilage and acetabular labrum, and eventually osteoarthritis. • It can cause a decrease in the length of the abductor lever arm resulting in additional abductor muscle force requirement. • May cause increased hip and knee adduction moments, an intoeing gait and patellofemoral maltracking, with resultant knee pain and arthritis. 16
  • 17.
    Sreeraj S R RETROVERSION • Femoralretroversion can cause damage to the labrum and articular cartilage, due to impingement between the femoral neck and acetabulum leading to osteoarthritis of the hip. • An increased risk of slipped capital femoral epiphysis • Susceptibility to a traumatic posterior hip dislocation. • Residual, untreated femoral retroversion may be a reason why hip preserving surgeries may fail, especially after the arthroscopic treatment of hip impingement. 17
  • 18.
    Sreeraj S R COAPTATION OFTHE ARTICULAR SURFACES • In the neutral or standing position, the articular surface of the femoral head remains exposed anteriorly and somewhat superiorly. • Not a true physiological position of the hip joint. (Kapandji) • Maximum articular contact of the head of the femur with the acetabulum is obtained when the femur 18 Levangie PK, Norkin CC
  • 19.
    Sreeraj S R COAPTATION OFTHE ARTICULAR SURFACES • The stability of the hip joint is assisted by gravity, in the straight position by opposing forces (ascending white arrow) opposite to the body weight (descending white arrow). • The acetabular labrum, widens and deepens the acetabulum (black arrows), setting the stage for a fibrous interlocking and retaining system. • The labrum retains the femoral head with the help of the zona orbicularis of the fibrous capsule , which holds the femoral neck 19 https://en.wikipedia.org/wiki/Zona_orbicul Kapandji AI
  • 20.
    Sreeraj S R COAPTATION OFTHE ARTICULAR SURFACES • Atmospheric pressure plays an important part in securing the articular coaptation of the hip joint. • The acetabular fossa may be important in setting up a partial vacuum in the joint so that atmospheric pressure contributes to stability by helping maintain contact between the femoral head and the acetabulum. 20 Kapandji AI acetabular fossa
  • 21.
    Sreeraj S R COAPTATION OFTHE ARTICULAR SURFACES • The periarticular ligaments and muscles are vital in maintaining the coaptation of the articular surfaces. • Their functions are reciprocally balanced. (Figure horizontal section) • Thus anteriorly the muscles are very few (blue arrow) and the ligaments (black arrows) are strong, while posteriorly the muscles (red arrow) predominate. • This coordinated activity keeps the femoral head (green arrow) closely applied to the 21 Kapandji AI
  • 22.
    Sreeraj S R COAPTATION OFTHE ARTICULAR SURFACES • Tensed ligaments in extension are efficient in securing coaptation. • In flexion the ligaments are slack, and the opposite happens. • This mechanism can be easily understood using the mechanical model, where a. parallel strings run between two wooden circles b. When one circle is rotated relative to the other, they are brought closer together. 22Kapandji AI extension flexion
  • 23.
    Sreeraj S R COAPTATION OFTHE ARTICULAR SURFACES • The position of flexion is a position of instability for the hip joint because of the slackness of the ligaments. • Flexion with adduction as in legs crossed position is easy to cause a posterior dislocation of the hip joint on a femoral impact. • Dashboard injury 23 Kapandji AI
  • 24.
    Sreeraj S R THE ARTICULARCAPSULE • The capsule is attached proximally to the entire periphery of the acetabulum beyond the acetabular labrum. • Fibers near the proximal attachment forms a tight ring just below the femoral head known as the zona orbicularis. 24
  • 25.
    Sreeraj S R THE ARTICULARCAPSULE • It is like a cylindrical sleeve helps to unite the articular surfaces • Made up of four types of fibres: 1. Longitudinal fibres, run parallel to the axis of the cylinder 2. Oblique fibres, spiral around the cylinder 3. Arcuate fibres, attached to the hip bone and forming an arc whose apex lies towards the middle of the sleeve. 4. Circular fibres, which are particularly abundant in the middle of the capsule and form the zona orbicularis (Weber's 25 Kapandji AI
  • 26.
    Sreeraj S R THE LIGAMENTS •The hip joint is reinforced by four ligaments, of which three are extracapsular and one intracapsular. • The extracapsular ligamen ts are the iliofemoral, pubofemoral, and ischiofemoral ligaments. • The intracapsular ligament , the ligamentum teres, is attached to the acetabular 26 https://en.wikipedia.org/wiki/Hip#Ligaments
  • 27.
  • 28.
    Sreeraj S R THE LIGAMENTS •During the change from the quadruped to the biped erect posture the pelvis moved into a position of extension relative to the femur • This made all the ligaments coiled around the femoral neck in the same direction. • Thus extension winds the ligaments around the neck more, tightening them, 28
  • 29.
    Sreeraj S R ROLE OFTHE LIGAMENTS IN EXTENSION • During hip extension: • all the ligaments become taut especially the inferior band of the iliofemoral ligament. • Thus responsible for checking the posterior tilt of the pelvis. 29 Example: the iliac bone rotates backwards while the femur sta
  • 30.
    Sreeraj S R ROLE OFTHE LIGAMENTS IN FLEXION • During hip flexion: • All the ligaments are relaxed • This relaxation of the ligaments is one of the factors responsible for the instability of the hip in this position. 30 Example: the iliac bone tilts forward while the femur stays
  • 31.
    Sreeraj S R ROLE OFTHE LIGAMENTS IN LATERAL ROTATION • During lateral rotation of the hip: • all the anterior ligaments running horizontally, i.e. the superior band of the iliofemoral and pubofemoral are taut. • and slackening of the ischio femoral ligament 31
  • 32.
    Sreeraj S R ROLE OFTHE LIGAMENTS IN MEDIAL ROTATION • During medial rotation: • all the anterior ligaments running horizontally are slackened, • while the ischiofemoral ligament becomes taut • The vertical inferior band of the iliofemoral ligament limits medial rotation, when the hip is in extension. 32
  • 33.
    Sreeraj S R ROLE OFTHE LIGAMENTS IN ADDUCTION • The superior band is tightened considerably, • the inferior band only slightly, • pubofemoral ligament relaxes. • The ischiofemoral ligament is stretched during adduction 33 Ischiofemoral
  • 34.
    Sreeraj S R ROLE OFTHE LIGAMENTS IN ABDUCTION • The pubofemoral ligament is tightened considerably • The superior and the inferior bands are relaxed. • The ischiofemoral ligament tenses up during abduction. 34 Ischiofemoral
  • 35.
    Sreeraj S R ROLE OFTHE LIGAMENTUM TERES • A strong intrinsic stabilizer that resists joint subluxation forces. • It is most taut when the hip is in its least stable positions i.e. flexion, adduction, and external rotation. • Adduction is the only position where the ligament is really under tension. • And is lax in hip abduction and internal rotation. 35 Cerezal L, Kassarjian A, Canga A, et al. Anatomy, Biomechanics, Imaging, and Management of Ligamentum Teres Injuries. RadioGraphics. 2010;30(6):1637-1651. doi:10.1148/rg.306105516
  • 36.
    Sreeraj S R CAPSULOLIGAMENTOUS TENSION •Hip joint extension, with slight abduction and medial rotation, is the close-packed position for the hip joint. • The capsuloligamentous tension at the hip joint is least when the hip is in moderate flexion, slight abduction, and midrotation. • In this position, the normal intra-articular pressure is minimized, and the capacity of the synovial capsule to accommodate abnormal amounts of fluid is greatest. • This is the position assumed by the hip when there is pain arising from capsuloligamentous problems or from excessive intra-articular pressure caused by extra fluid (blood or synovial fluid) in the joint. 36
  • 37.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING - FEMUR • The trabeculae are calcified plates of tissue within the cancellous bone as a result of interaction between mechanical stresses and structural adaptation created by the transmission of forces between bones. • The trabeculae line up along lines of stress and form systems that normally adapt to stress requirements. 37
  • 38.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING - FEMUR • The HAT loads the head of the femur, • The GRF comes up the shaft of the femur, • resulting in a moment arm (MA) • This bending moment creates tensile stress on the superior aspect of the femoral neck and compressive stress on the inferior aspect. 38
  • 39.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING - FEMUR • A complex set of adaptive forces prevents the rotation and resists the shear forces that the force couple causes; • These forces are the structural resistance of two major and three minor trabecular systems • Two major are the medial compressive and lateral tensile trabecular systems. 39
  • 40.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING - FEMUR • The zone of weakness is an area in the femoral neck in which the trabeculae are relatively thin and do not cross each other. • The zone of weakness of the femoral neck is particularly susceptible to the bending forces across the area and can fracture as it has less reinforcement and thus more potential for failure. 40
  • 41.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING - FEMUR • Changes in trabecular patterns due to altered angle. • Coxa valga leads to more compression trabeculae, coxa vara to more tension trabeculae. 41
  • 42.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING - FEMUR • The forces of HAT and the ground reaction force also act on the femoral shaft. • As the shaft of the femur lies at an angle instead of vertical, • loading on the oblique femur results in bending stresses in the shaft. • The medial cortical bone of the femoral shaft (diaphysis) must resist compressive stresses, whereas the lateral cortical bone must resist tensile stresses 42
  • 43.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING - ACETABULUM • The primary weight- bearing surface of the acetabulum, or dome of the acetabulum, is located on the superior portion of the lunate surface. • In the normal hip, the dome lies directly over the center of rotation of the femoral head. • Peak contact pressures during unilateral stance to be located near the dome. 43
  • 44.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING - ACETABULUM • Normal stress distribution can be altered; • with a lack of femoral head coverage by the acetabulum due to decreased center edge angle • Excessive acetabular anteversion 44 Coxa Valga Normal Coxa Vara
  • 45.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING – ARTICULAR CARTILAGE • The superior femoral head receives compression from • the dome in standing • from the posterior acetabulum in sitting and • the anterior acetabulum in extension. • Full loading of the hip joint ensures congruence and load distribution between the larger femoral head and the 45
  • 46.
    Sreeraj S R STRUCTURAL ADAPTATIONSTO WEIGHT BEARING – ARTICULAR CARTILAGE • Persisting incongruence of the acetabulum could result in; • incomplete compression of the dome cartilage and, • inadequate fluid exchange to maintain cartilage nutrition. • The articular cartilage is avascular, so it dependent on compression & release forces to move nutrients through the tissue; • Both too little compression and excessive compression can lead to compromise of the cartilage structure. 46
  • 47.
    Sreeraj S R MOTION OFTHE FEMUR ON THE ACETABULUM • The motions of the hip joint are the movement of the convex femoral head within the concavity of the acetabulum as the femur moves through its three degrees of freedom: 1. flexion/extension, 2. abduction/adduction, and 3. medial/lateral rotation. • The femoral head will glide within the acetabulum in a direction opposite to motion of the distal end of the femur. 47
  • 48.
    Sreeraj S R MOTION OFTHE FEMUR ON THE ACETABULUM • Flexion and extension of the femur occur as an almost pure spin of the femoral head around a coronal axis. • However, flexion and extension from other positions (e.g., in abduction or medial rotation) must include both spinning and gliding of the articular surfaces, depending on the combination of motions. • The motions of abduction/adduction and medial/lateral rotation must include both spinning and gliding of the femoral head within the acetabulum • The intra-articular motion occurs in a direction opposite to motion of the distal end of the femur. • For Example, The head spins posteriorly in flexion and48
  • 49.
    Sreeraj S R MOTION OFTHE FEMUR ON THE ACETABULUM • Flexion of the hip is generally about 120° with the knee flexed. • It is limited to 90° with the knee extended due to passive tension in the two joint hamstrings muscle group • Hip extension is considered to have a range of 10 ° to 30°. • When hip extension is combined with knee flexion, passive tension in the two-joint rectus femoris muscle may limit the movement. 49
  • 50.
    Sreeraj S R MOTION OFTHE FEMUR ON THE ACETABULUM • The femur can be abducted 45° to 50° and adducted 20° to 30°. • Abduction can be limited by the two-joint Gracilis muscle • Adduction limited by the Tensor Fascia Lata (TFL) muscle and its associated Iliotibial (IT) band. • Medial and lateral rotation of the hip are usually measured with the hip joint in 90° of flexion; the typical range is 42° to 50°. • Femoral anteversion is correlated with decreased range of lateral rotation and increased range of medial rotation. 50
  • 51.
    Sreeraj S R MOTION OFTHE FEMUR ON THE ACETABULUM • Normal gait on level ground requires at least the • following hip joint ranges: • 30° flexion, • 10° extension, • 5° of both abduction and adduction, and • 5° of both medial and lateral rotation. • Walking on uneven terrain or stairs increase the need for joint range. 51
  • 52.
    Sreeraj S R MOTION OFTHE PELVIS ON THE FEMUR • The motion of the pelvis are the same three degrees of freedom for the hip joint are accomplished by the pelvis rather than by the femur. • Anterior and posterior pelvic tilts are motions of the entire pelvic ring in the sagittal plane around a coronal axis. 52 A. The pelvis in its normal position in erect stance. B. Posterior tilting of the pelvis moves the symphysis pubis superiorly on the fixed femur. The hip joint extends. C. In anterior tilting, the anterior superior iliac spines move inferiorly on the fixed femur. The hip joint flexes.
  • 53.
    Sreeraj S R MOTION OFTHE PELVIS ON THE FEMUR • Lateral pelvic tilt is a frontal plane motion of the entire pelvis around an anteroposterior axis. • In the normally aligned pelvis, a line through the anterior superior iliac spines is horizontal. A. Hiking of the pelvis around the right hip joint results in right hip abduction. B. Dropping of the pelvis around the right hip joint 53
  • 54.
    Sreeraj S R MOTION OFTHE PELVIS ON THE FEMUR • Lateral Shift of the Pelvis can also occur in bilateral stance. • When the pelvis is shifted to the right in bilateral stance, the right hip joint adducted, and the left hip joint abducted. • To return to neutral position in same stance the right abductor and left adductor muscles work synergistically to shift the 54
  • 55.
    Sreeraj S R MOTION OFTHE PELVIS ON THE FEMUR • Pelvic Rotation is motion of the entire pelvic ring in the transverse plane around a vertical axis. • Rotation can occur both in bilateral stance as well as in single-limb support around the axis of the weight-bearing hip joint. 55 A. Forward rotation of the pelvis around the left hip joint results in medial rotation of the left hip joint. B. Neutral position of the pelvis and the left hip joint. C. Backward rotation of the pelvis around the left hip joint results in lateral rotation of the left hip joint.
  • 56.
  • 57.
    Sreeraj S R COORDINATED MOTIONSOF THE FEMUR, PELVIS, AND LUMBAR SPINE • When the pelvis moves on a relatively fixed femur, there are two possible outcomes to consider. 1. Either the head and trunk will follow the motion of the pelvis (moving the head through space) open chain responses or 2. The head will continue to remain relatively upright and vertical despite the pelvic motions, closed chain responses. 57
  • 58.
    Sreeraj S R COORDINATED MOTIONSOF THE FEMUR, PELVIS, AND LUMBAR SPINE • Pelvifemoral Motion is a coordinated movement of femur, pelvis, and spine to produce a larger ROM than is available to one segment alone. • The lower, caudal end of the axial skeleton is firmly attached to the pelvis by way of the sacroiliac joints. Therefore, rotation of the pelvis over the femoral heads typically changes the configuration of the lumbar spine. This important kinematic relationship is known as lumbopelvic rhythm • Predominantly an open-chain motion but not exclusive. • AIanalogous to scapulohumeral motion. 58
  • 59.
    Sreeraj S R COORDINATED MOTIONSOF THE FEMUR, PELVIS, AND LUMBAR SPINE 59
  • 60.
    Sreeraj S R COORDINATED MOTIONSOF THE FEMUR, PELVIS, AND LUMBAR SPINE • Closed-Chain Hip Joint Function is formed because both ends of the chain (both feet in this example) are “fixed” and movement at any one joint in the chain invariably involves movement at one or more other links in the chain. 60
  • 61.
    Sreeraj S R COORDINATED MOTIONSOF THE FEMUR, PELVIS, AND LUMBAR SPINE PELVIC MOTION HIP JOINT MOTION LUMBAR SPINE MOTION Anterior pelvic tilt Hip flexion Lumbar extension Posterior pelvic tilt Hip extension Lumbar flexion Lateral pelvic tilt (pelvic drop) Right hip adduction Right lateral flexion Lateral pelvic tilt (pelvic hike) Right hip abduction Left lateral flexion Forward rotation Right hip medial rotation Rotation to the left (in closed chain) Backward rotation Right hip lateral rotation Rotation to the right (in closed chain) 61
  • 62.
    Sreeraj S R MUSCLES OFTHE HIP • The line of pull of a muscle is the long axis of the muscle. • The angle of pull is the angle between the long axis of the bone (lever arm) and the line of pull of the muscle. • The angle of pull and moment arm of the muscle both change as the joint goes through its range of motion. 62 A lateral view shows the sagittal plane line of force of several hip muscles.
  • 63.
    Sreeraj S R MUSCLES OFTHE HIP • A muscle action describes the potential direction of rotation of the joint following its activation • A muscle torque describes the “strength” of the action. • A muscle torque can be estimated by the product of the muscle force (in Newtons) and the muscle’s associated moment arm length (meters). 63
  • 64.
    Sreeraj S R HIP FLEXORS •Primary 1. Iliopsoas 2. Rectus femoris 3. Sartorius 4. Tensor fasciae latae 5. Pectineus • Secondary 1. Adductor brevis 2. Gracilis 3. Gluteus minimus (anterior fibers) 64
  • 65.
  • 66.
  • 67.
  • 68.
  • 69.
  • 70.
    Sreeraj S R PELVIC-ON-FEMORAL HIPFLEXION • The anterior pelvic tilt is performed by a force-couple between the hip flexors and low-back extensor muscles. • Any muscle capable of hip flexion is equally capable of tilting the pelvis anteriorly. • Also note a consequent increase in lordosis at the lumbar spine. • Greater lordosis increases the compressive loads on the lumbar apophyseal joints and shear force at the lumbosacral junction. 70
  • 71.
    Sreeraj S R FEMORAL-ON-PELVIC HIPFLEXION • Open chain action. • The synergistic action of one representative abdominal muscle (rectus abdominis) in SLR. A. With normal activation of the abdominal muscles, the pelvis is stabilized and prevented from anterior tilting by the downward pull of the hip flexor muscles. B. With reduced activation of the abdominal muscles, contraction of the hip flexor muscles is shown producing a 71
  • 72.
    Sreeraj S R HIP ADDUCTORS •Primary 1. Pectineus 2. Adductor longus 3. Gracilis 4. Adductor brevis 5. Adductor magnus • Secondary 1. Biceps femoris (long head) 2. Gluteus maximus (lower fibers) 3. Quadratus femoris 72
  • 73.
  • 74.
  • 75.
  • 76.
  • 77.
  • 78.
    Sreeraj S R HIP ADDUCTORS 78 Theanatomic organization and proximal attachments of the adductor muscle group.
  • 79.
    Sreeraj S R FRONTAL PLANEFUNCTION IN HIP ADDUCTION • The bilateral cooperative action of selected adductor muscles. • Example: kicking a soccer ball. • The left adductor magnus is shown actively producing pelvic - on - femoral adduction. • Several right adductor muscles are shown actively producing femoral - on - pelvic adduction 79 There is concentric activation of the left adductor muscles and eccentric activation of the left gluteus medius to decelerate and control the motions.
  • 80.
    Sreeraj S R SAGITTAL PLANEFUNCTION IN HIP ADDUCTION • Adductor muscles are considered flexors from the extended position. • When outside the 400 to 700 flexed position, the individual adductor muscles regain leverage as significant extensors of the hip. • From a hip position of near extension, the line of force of the adductor longus is well anterior to the medial-lateral axis of rotation. • The adductor longus now has a flexor moment arm and 80 These contrasting actions are based on the change in line of force of the adductor longus, relative to the medio lateral axis of rotation at the hip.
  • 81.
    Sreeraj S R HIP INTERNALROTATORS • Primary Not applicable • no muscle with any potential to internally rotate the hip lies even close to the horizontal plane. From the anatomic position, therefore, it is difficult to assign any muscle as a primary internal rotator of the hip. • Secondary 1. Gluteus minimus (anterior fibers) 2. Gluteus medius (anterior fibers) 3. Tensor fasciae latae 4. Adductor longus 5. Adductor brevis 6. Pectineus 7. Piriformis 81
  • 82.
    Sreeraj S R HIP INTERNALROTATORS • A superior view depicts the horizontal plane line of force of several muscles that cross the hip. • The external rotators are indicated by solid lines and • the internal rotators by dashed lines. 82
  • 83.
    Sreeraj S R HIP INTERNALROTATORS • The adductor muscles as secondary internal rotators of the hip. A. Because of the anterior bowing of the femoral shaft, a large segment of the linea aspera runs anterior to the longitudinal axis of rotation. B. A superior view of the right hip shows the horizontal line of force of the adductor longus causes an internal rotation torque by producing a force that passes anterior to the axis of rotation 83
  • 84.
    Sreeraj S R HIP EXTENSORS •Primary 1. Gluteus maximus 2. Biceps femoris (long head) 3. Semitendinosus 4. Semimembranosus 5. Adductor magnus (posterior head) • Secondary 1. Gluteus medius (posterior fibers) 2. Adductor magnus (anterior head) 84 With the hip flexed to at least about 70 degrees and beyond, most adductors muscles except pectineus can assist with hip extension.
  • 85.
  • 86.
  • 87.
  • 88.
    Sreeraj S R PELVIC-ON-FEMORAL HIPEXTENSION PERFORMING A POSTERIOR PELVIC TILT • The force couple between representative hip extensors and abdominal muscles used to posteriorly tilt the pelvis. • Note the decreased lordosis at the lumbar spine. • The extension at the hip stretches the iliofemoral ligament. 88
  • 89.
    Sreeraj S R PELVIC-ON-FEMORAL HIPEXTENSION CONTROLLING A FORWARD LEAN OF THE BODY 89 A. Slight forward lean of the upper body displaces the body weight force slightly anterior to the medial- lateral axis of rotation at the hip. • This slightly flexed posture is restrained by minimal activation from the gluteus maximus and hamstring muscles.
  • 90.
    Sreeraj S R PELVIC-ON-FEMORAL HIPEXTENSION CONTROLLING A FORWARD LEAN OF THE BODY 90 B. A more significant forward lean displaces the body weight force even farther anteriorly. • The greater flexion of the hips rotates the ischial tuberosities posteriorly, thereby increasing the hip extension moment arm of the hamstrings. • The gluteus maximus, however, remains relatively inactive in this position • The taut line (with arrowhead within the stretched hamstring muscles) indicates the increased passive tension.
  • 91.
    Sreeraj S R FEMORAL-ON-PELVIC HIPEXTENSION • Consider the example of climbing a steep hill carrying a heavy pack. • The flexed position favours greater extension torque generation from the hip extensor muscles and many of the adductor muscles. • The flexed position of the right hip also imposes a large external (flexion) torque at the hip. 91 Activation is also required in low-back extensor muscles to stabilize the position of the pelvis.
  • 92.
    Sreeraj S R HIP ABDUCTORS •Primary 1. Gluteus medius 2. Gluteus minimus 3. Tensor fasciae latae • Secondary 1. Piriformis 2. Sartorius 92
  • 93.
  • 94.
  • 95.
  • 96.
    Sreeraj S R HIP ABDUCTORS •The gluteus medius and minimum have been likened to the “rotator cuff” of the hip, with the supraspinatus and subscapularis, respectively. • Also analogous to the deltoid muscle of the glenohumeral joint. • the anterior fibers of the gluteus medius are active in hip flexion and • the posterior fibers function during extension. • In the neutral hip, • the posterior portion of the medius will produce a lateral rotational moment and • the middle and anterior portions have small medial96
  • 97.
    Sreeraj S R HIP ABDUCTORMECHANISM: CONTROL OF FRONTAL PLANE STABILITY OF THE PELVIS DURING WALKING • During the stance phase the hip abductor muscles have a role in controlling the pelvis in the frontal plane and the horizontal plane. • During the single-limb support phase of gait the opposite leg is off the ground and swinging forward. • Without adequate abduction torque on the stance limb, the pelvis and trunk may drop uncontrollably toward the side of the swinging limb. 97
  • 98.
    Sreeraj S R HIP ABDUCTORMECHANISM: ROLE IN THE PRODUCTION OF COMPRESSION FORCE AT THE HIP • The counterclockwise torque (solid circle) is the product of the right hip abductor force (HAF) times internal moment arm (D) • The clockwise torque (dashed circle) is the product of body weight (BW) times external moment arm (D1). • Because the system is assumed to be in equilibrium, the torques in the frontal plane are equal in magnitude and opposite in direction: • HAF × D = BW × D1. 98 The illustration assumes that the pelvis and trunk are in static (linear and rotary) equilibrium about the right hip.
  • 99.
    Sreeraj S R HIP ABDUCTORMECHANISM: ROLE IN THE PRODUCTION OF COMPRESSION FORCE AT THE HIP • Note that the internal moment arm (D) used by the hip abductor muscles is about half the length of the external moment arm (D1) used by body weight. • So, hip abductor muscles must produce a force twice that of body weight in order to achieve stability during single-limb support. • This downward force is counteracted by a joint reaction force (JRF) of equal magnitude oriented in nearly the opposite direction. • The JRF angulation is strongly 99
  • 100.
    Sreeraj S R HIP EXTERNALROTATORS • Primary 1. Gluteus maximus 2. Piriformis 3. Obturator internus 4. Gemellus superior 5. Gemellus inferior 6. Quadratus femoris • Secondary 1. Gluteus medius (posterior fibers) 2. Gluteus minimus (posterior fibers) 3. Obturator externus 4. Sartorius 5. Biceps femoris (long head) 100
  • 101.
  • 102.
  • 103.
    Sreeraj S R PELVIC-ON-FEMORAL HIPEXTERNAL ROTATORS • With the right lower extremity firmly in contact with the ground, contraction of the right external rotators accelerates the anterior side of the pelvis and attached trunk to the left - contralateral to the fixed femur. • This action of planting a foot and “cutting” to the opposite side is the natural way to abruptly 103
  • 104.
    Sreeraj S R HIP ROTATORS •The piriformis, reportedly an external rotator in full extension but an internal rotator at 90° or more of flexion. • Restrictions in the extensibility of this muscle are typically described as limiting passive hip internal rotation, and possibly compressing the underlying sciatic nerve. • A traditional method for stretching a tight piriformis is to combine full flexion and external rotation of the hip, typically performed with the knee flexed. 104
  • 105.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE BILATERAL STANCE • In erect bilateral stance, • both hips are in neutral and • weight is evenly distributed between both legs. • The line of gravity falls just posterior to the axis for flexion/extension of the hip joint. • The posterior location of the line of gravity creates an extension moment of force around the hip which is largely checked by passive tension in the hip joint capsuloligamentous structures and activity of hip flexors. • In the frontal plane, the body weight is transmitted through the sacroiliac joints and pelvis to the right and left femoral heads. 105
  • 106.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE BILATERAL STANCE • DR & DL : the gravitational moment arms • WR & WL : body weight • Because WR = WL • Magnitude of gravitational torque around hip is: WR X DR = WL X DL • Total hip joint compression = 4/6 X body weight 106
  • 107.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE BILATERAL STANCE • In normal B/L stance, assuming no muscular forces maintain either sagittal or frontal plane stability at the hip joint, • the compression across each hip joint should be half the superimposed body weight • or one third of HAT to each hip. • Example: Assuming a body weight of 84 Kg. • The weight of HAT is 4/6 body weight. • 84 X 4/6 = 56 Kg. • Each hip receives 56/2 = 28 Kg. HAT: Head Arm Trunk 107
  • 108.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE UNILATERAL STANCE • Full superimposed body weight (HAT) is being supported by the right hip joint. • The weight of the non- weight bearing left limb must now be supported along with the weight of HAT. • The magnitude of body weight (W) compressing the right hip joint is [4/6 X W] + [1/6 X W] 108
  • 109.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE UNILATERAL STANCE Example: Assuming a body weight of 84 Kg. • The magnitude of body weight (W) compressing the right hip joint is [4/6 X W] + [1/6 X W] • 4/6 X 84 + 1/6 X 84 • 56 + 14 = 70 • So right hip joint compression body weight is 70 Kg • Now the hip joint in unilateral stance being compressed by body weight (gravity) concomitantly creating a torque around the hip joint. 109
  • 110.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE UNILATERAL STANCE • The force of gravity acting on HAT and the non weight bearing left lower limb (HATLL) will create an adduction torque around the weight-bearing hip joint ( drop of non weight bearing limb) and an abduction counter torque by the hip abductor musculature. • The result will be joint compression or a joint reaction force that is a combination of both body weight and abductor muscular compression. 110
  • 111.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE UNILATERAL STANCE Example: Assuming a body weight of 84 Kg. • So right hip joint compression body weight is 70 Kg • Add./LOG MA is 10 cm = 0.1m • Abd. MA is 5 cm = 0.05 m • HATLL torque add. = 70 X 0.1 = 7 Kg • So torque abd. = Torque Add./ Abd. MA = 7/0.05 = 140 Kg • The total hip joint compression, or joint reaction 111
  • 112.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE COMPENSATORY LATERAL LEAN OF THE TRUNK • When the trunk is laterally flexed toward the stance limb, the moment arm of HATLL is substantially reduced. • The compensatory lateral lean of the trunk toward the painful stance limb will swing the line of gravity closer to the hip joint, thereby reducing the gravitational moment arm 112
  • 113.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE COMPENSATORY LATERAL LEAN OF THE TRUNK Example: Assuming a body weight of 84 Kg. • So right hip joint compression body weight is 70 Kg • Add./LOG MA is 2.5 cm = 0.025m • Abd. MA is 5 cm = 0.05 m • HATLL torque add. = 70 X 0.025 = 1.75 Kg • So torque abd. = Torque Add./ Abd. MA = 1.75/0.05 = 35 Kg • The total hip joint compression, or joint reaction force is abd. torque + HATLL 113
  • 114.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE USE OF A CANE IPSILATERALLY • Pushing downward on a cane held in the hand on the side of pain or weakness should reduce the superimposed body weight by the amount of downward thrust; • that is, some of the weight of HATLL would follow the arm to the cane, rather than arriving on the sacrum and the weight-bearing hip joint. • The proportion of body weight that passes through the cane will not pass through the hip joint and will not create an adduction torque around the supporting hip joint. 114
  • 115.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE USE OF A CANE IPSILATERALLY Example: Assuming a body weight of 84 Kg. • If 84 kg push down on the kane with 15% BW = 84 X 0.15 = 12.6 will pass through kane • So the magnitude of HATLL is 70 – 12.6 = 57.4 • So right hip joint compression body weight is 57.4 Kg • Add./LOG MA is 10 cm = 0.1m • Abd. MA is 5 cm = 0.05 m • HATLL torque add. = 57.4 X 0.1 = 5.74 Kg • So torque abd. = Torque Add./ Abd. MA = 5.74/0.05 = 114 Kg • The total hip joint compression, or joint reaction force is abd. torque + HATLL W • i.e. 114 + 57.4 = 172.2 Kg 115
  • 116.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE USE OF A CANE CONTRALATERALLY • When a cane is placed in the hand opposite the painful supporting hip, the weight passing through the right hip is reduced. • Activation of the left latissimus dorsi provides a counter torque to that of HATLL and diminishes the need for a contraction of the right hip abductors. • In this example the MA of the cane is estimated to 116
  • 117.
    Sreeraj S R HIP JOINTFORCES AND MUSCLE FUNCTION IN STANCE USE OF A CANE CONTRALATERALLY Example: Assuming a body weight of 84 Kg. • If 84 kg push down on the kane with 15% BW = 84 X 0.15 = 12.6 will pass through kane • So the magnitude of HATLL is 70 – 12.6 = 57.4 • So right hip joint compression body weight is 57.4 Kg • Adduction/LOG MA is 10 cm = 0.1m • Abduction MA is 50 cm = 0.5 m • HATLL torque add. = 57.4 X 0.1 = 5.74 Kg • Cane torque = 12.6 X 0.5 = 6.3 • If assume that the gravitational adduction torque and the counter torque provided by the cane offset each other there would be no need for hip abductor muscle force • The total hip joint compression, or joint reaction force is abd. torque + HATLL W 117
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  • 119.
    Sreeraj S R REFERENCES 1. MartinRL, Kivlan B. The Hip Complex. In: Levangie PK, Norkin CC, editors. Joint structure and function : a comprehensive analysis. 5th ed. Philadelphia, Pa: F.A. Davis Company; 2011. p. 356–94. 2. Kapandji AI. The Hip. In: Physiology of the Joints: Volume 2 Lower Limb. 6th ed. Edinburgh ; New York: Churchill Livingstone/Elsevier; 2011. p. 2–65. 3. Uritani D, Fukumoto T. Differences of Isometric Internal and External Hip Rotation Torques among Three Different Hip Flexion Positions. Journal of Physical Therapy Science. 2012;24(9):863-865. doi:10.1589/jpts.24.863 4. Neumann DA. Kinesiology of the Hip: A Focus on Muscular Actions. Journal of Orthopaedic & Sports Physical Therapy. 2010 Feb;40(2):82–94. 5. Therapeutic Exercise for Musculoskeletal Injuries [Internet]. [cited 2020 Feb 4]. Available from: https://humankinetics.com/AcuCustom/Sitename/DAM/153/Houglum_78-79.pdf 6. Lippert L. Chapter 17 Hip. In: Clinical kinesiology and anatomy. 4th ed. Philadelphia: F.A. Davis Company; 2006. p. 233–49. 119