The hip joint is a "ball and socket" joint. The "ball" is the head of the femur, or thigh bone, and the "socket" is the cup shaped acetabulum. The joint surface is covered by a smooth articular surface that allows pain free movement in the joint.
Total hip replacement is a surgical procedure in which the damaged cartilage and bone is removed from the hip joint and replaced with artificial components. The hip joint is one of the body's largest weight-bearing joints, located between the thigh bone (femur) and the pelvis (acetabulum).