Structure of a Normal Hip Joint
The hip is the body’s second largest weight-bearing joint (after the knee). It is a ball and socket variety of synovial joint. The rounded head of the femur (thighbone) forms the ball, which fits into the acetabulum (a cup-shaped socket in the pelvis). Ligaments connect the ball to the socket and usually provide tremendous stability to the joint. The hip joint is normally very sturdy because of the fit between the femoral head and acetabulum as well as strong ligaments and muscles at the joint.
The femoral head and the acetabular cavity are covered with articular cartilage, a smooth tissue that cushions the bones and enables them to move easily. The joint is enclosed in joint capsule. From inside, the joint capsule has a layer of synovial membrane, a thin, smooth tissue liner. This membrane releases a synovial fluid that lubricates the hip and almost eliminates the friction. Acetabular Labrum is a ring-shaped cartilaginous sealing forms the edge of this bony socket. It keeps the synovial fluid under constant tension inside the joint and thus distributes joint stresses all over the joint equally.
Normal Hip Joint
Hip is placed deep inside the groin and covered by number of muscles all around. Due to its natural structure and placement, hip joint is the most stable joint in the body.