Anatomy of the Hip
The hip is a ball-and-socket joint. At the top of the femur (thigh bone) is the femoral head (ball). The femoral head rests inside the acetabulum (socket), which is an important part of the pelvis bone. The femoral head and acetabulum are covered with smooth articular cartilage (joint surface). Around the edge of the acetabulum is a rubbery rim of tissue called the labrum, which deepens the hip socket and protects the joint surface. The hip joint itself is completely enclosed in a tough layer of tissue called the joint capsule, which keeps fluid inside the hip joint. The hip bones, the joint capsule, and surrounding muscles all help to stabilise and move the hip joint.