The largest joint in the body, the hip is composed of the large, round head of the femur which lies within the acetabulum or cup of the pelvis. Cartilage covers the articular surfaces, as in every other joint. There is a joint capsule and a number of muscles which cross and protect the joint and allow movement in a number of planes.
The blood supply to the hip is relatively meager and easily disrupted with trauma.
Since the entire weight of the body goes through this joint with every step, it is vulnerable to damage from use and is a common site for degenerative joint disease.