Hip joint (biomechanics)


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Hip joint (biomechanics)

  1. 1. HIP JOINT The weight bearing joint, in which there is articulation of head of the femur and the acetabulum of pelvic bone. MUSCULATURE OF HIP JOINT: Like all other joints hip joint is also supported by muscles. They cause the movement of the joint and give support to the joint. Different muscles work in different way in different positions. Like the adductor muscles maybe hip flexors in neutral position but maybe hip extensors when the hip is flexed MOVEMENTS AT HIP JOINT: Hip abduction/adduction Hip flexion/extension Hip medial/lateral rotation HIP MUSCLES: Flexors Extensors Abductors Adductors Medial rotators Lateral rotators
  2. 2. FLEXORS: 1) Sarotrius 2)ilopsoas 3) Rectus femoris ILIACUS MUCLCE: ORIGIN:Iliac fossa of the hip bone INSERTION:With psoas into the lessor trochanter of the femur. PSOAS MUSCLE: ORIGION:Transverse process, bodies and intervertebral discs of the 12th thoracic and five lumber vertebrae. Insertion:Withiliacus into lessor trochanter of the fumer. COMBINE ACTION OF ILIACUS AND PSOAS MUCLE: Flexes thigh on trunk,if thigh is fixed it flexes the trunk on the thigh as in sitting up from lying down. This muscle combine cause hip flexion and extrernal rotation. Unilateral action of these mucle cause trunk lateral roation. Bilateral action of these muclse cause raising of the trunk from the fully supine position. Iliacus muscle cause flexion and psoas mucles cause flexion and lateral roation of lumber spine. RECTUR FEMORIS: ORIGION: STRAIGHT HEAD:Anteriorintferior iliac spine.
  3. 3. REFLECTED HEAD:Ilium above acetabulum. INSERTION:Quadriceps tendon into patella, then via ligamentum patella into tubercle of tibia. ACTION: Cause function on both hip joint and on knee. It cause hip flexion and knew extension. ACTIVE INSUFFICIENCY: During hip flexion and knee extension,a point come where no more flexion of hi joint occurs,due to the active insufficiency of recturfemoris muscle. At the same time the action is stopped by the hamstring muscle because of its passive insuffiency. Passive insufficiency is actually the pint where no more extension of a muscle can occur. SARTORIUS: Anterior superior iliacspine. ORIGION:Anterior superior iliacspine. INSERTION:Upper medial surface of shaft of tibia. ACTION: This muscle has so many functions at hip and knee joint. The tailor sitting/ cross sitting is actually due to this muscle During cross sittion there is flexion at hip and knew joint At the same time lateral rotation of thigh at hip joint and medial roation of leg at knew joint.
  4. 4. TENSOR FASCIA LATA: ORIGION:Iliac crest INSERTION:Iliotibialtract,,it is the thickening of the fascia lata on the laterally ACTION: This mucle cause three main functions, Flexion of thigh at hip joint, abduction and medially rotation. The Iliotibial tract and tensor fascia lata are stretchable, they assist in tensile force and prevent femur from fracturing, as we know bone can bear compressive for rather than tensile. SECONDARY HIP FLEXORS: Pectinius, adductor longus, adductor magnus and gracilis. These muscles cause 40-50% flexion of hip joint. Gracilis is active when there is hip flexion and knee extension. ADDUCTORS: Adductors of the hip joint are: Gracilis,adductormagnus,adductorbrevis,adductorlongus. main action of these mucles is : they laterally rotates thigh at hip joint and assists in lateral rotation.
  5. 5. Adductor longus,brevis and posterior adductor magnus muscles have only small movement arms for medial rotation Gracilis and anterior adductor magnus have smaller moment arm for lateral rotation. Gracilismuscle also cause knee flexion. EXTENSORS: The main extensors of the hip joint are: Gluteus maximus and hamstring muscles GLUTEUS MSUCLE: This is the longest mescle with mass 12.5% of total body muscles. It is the main extensor of the hip joint. It is the main mucles which can bear weight more then human body Its moment arm is more than both posterior adductor magunus muscle and that of gracilis. HAMSTRINGS: There are three two joint mucles in hamstrings: Semitendinosus,semimembranosus and biceps femoris. They assist up to 35% for hip extension when the hip is flexed. These mucles also cause knee flexion that’s why they are considered very important. Their combine strength is yet not more than gluteus maximus. ABDUCTORS: The main abductors are: Gluteus medius and gluteus minimus
  6. 6. Glutiusmedius: like the deltoid muscle it has three man prats; anterioir ,posterior and middle the anterior fibers are active during hip flexion and posterior function in hip extension. In neutral position, posterior fibers cause lateral rotation while anterioir and middle cause medial rotation. All the mucles fibers of gluteus medius combine cause abduction of hip joint. GLUTIUS MINIMUS: This mucle cause main abduction but also play role in hip flexion. It can cause medial rotation. It combines with gluteus medius and cause abduction of hip. Lateral rotators: These include: Superior gemilus,interiorgemilus , obturatorexternus and internus , piriforimis and quadratusfemoris. Piriforimis has a large moment arm,it cause lateral rotation at 0 degree flexion but cause medial rotation at 90 degree flexion. The obturatorexternus and the quadratusfemoris do not dimish their lateral rotation for flexion, they have comparative small moment arm. All these muscles like the rotator cuff are considered the joint compressors because their combine moment arm is parallel to the head and neck of the femur.
  7. 7. MEDIAL ROTATORS: There are no primary muscles for medial rotation of hip joint. Medial rotation can be caused by secondary muscles like: Gluteus medius,minimus and tensor fascia lata. Medial rotation can occur three times more in flexion than in extension.