Biomechanics of the hip joint

The hip joint biomechanics has been investigated for decades due to the clinical relevance of its disorders such as osteoarthritis and femoral neck fracture, which are common in elderly subjects and associated with severe pain and disability. From a mechanical point of view, the hip joint is a typical “ball-and-socket” joint, with the femoral head acting as the ball and the acetabulum as the socket. The bony surfaces in contact are covered by a layer of articular cartilage with spatially variable thickness and mechanical properties. The hip is a synovial joint, that is, its articular surfaces are surrounded by a fibrous capsule and a synovial membrane; the joint cavity is filled by synovial fluid secreted by the synovial membrane, which reduces the articular friction. The stability of the hip joint is enhanced by a strong ligamentous system formed by the iliofemoral, ischiofemoral, and pubofemoral ligaments, and by the acetabular labrum, a robust fibrocartilaginous structure covering the bony margin of the acetabulum. The labrum poses a high resistance to fluid flow and seals the hip joint by preventing fluid loss even in highly pressurized scenarios, enhancing stability and further reducing friction.SCOPUS: ch.b