BIOMECHANICS OF hip

PresentedBy

Dr. Nazish RafiqueLecturer

ZCPT

Function of HipThe primary function of the hip joint

is to support the weight of the head, arms, and trunk (HAT) both in static erect posture and in dynamic postures such asAmbulation,Running,Stair climbing.

Structure of HipThe hip joint or coxofemoral joint

Articulation with the acetabulum of the pelvis and the head of the femur

Ball-and-socket joint

Synovial joint

Bones of HipIliumIschiumPubisFemur

The acetabulum is formed by the pubis, ischium and ilium bones

The pubis forms one fifth of the acetabulum

The ischium forms two fifths

The ilium forms the remainder

Femoral Head

The head of the femur, which forms approximatelytwo-thirds of a sphere.

Acetabulum Acetabular surface is covered with

articular cartilage that thickens peripherally and laterally

Osseous acetabulum is deep and provides static stability

Acetabular cavity is deepened by the labrum, flat rim of fibrocartilage, transverse acetabular ligament

Center edge (CE) angle / angle of Wiberg

A line connecting the lateral rim of the acetabulum and the center of the femoral head.

This line forms an angle with the vertical

The amount of inferior tilt of the acetabulum.

CE angles in adults to average 38º in men and 35º in women

The entire periphery of the acetabulum is rimmed by a ring of wedge-shaped fibrocartilage

Hydrostatic fluid pressure within the intra-articular space was greater within the labrum than without,

The labrum may also enhance joint lubrication if the labrum adequately fits the femoral head.

Removal of the transverse acetabular ligament and labrum did not affect the loading pattern of the acetabulum

Acetabular labrum

Joint CapsuleStrong fibrous sleeveAnteriorly

Proximally to the bone surrounding the acetabulum.

Distally to the trochanteric linePosteriorly

To the margins of the acetabulum and surrounding bone

Neck of the femur- not to the trochanteric crest

Joint CapsuleThe capsule is thickened anterosuperiorly,

where the predominant stresses occurRelatively thin & loosely attached

posteroinferiorlyThe femoral head & neck is intracapsular,Both the greater & lesser trochanters are

extracapsular.The synovial membrane lines the inside of

the capsule.

Joint CapsuleIntrinsic stability is provided by the

congruency of joint structure, and ligamentous support

Prone to dislocation in a position of flexion , abduction and internal rotation (dashboard injury)

Posterior capsule is relatively weakerClose packed position is extension/

abduction/ internal rotation and flexion (90º)/ abduction/ external rotation