Hip replacement. Artwork of the pelvis of a person who has had a hip replacement. The prosthetic hip joint consists of a metal shaft and ball attached to the top of the femur and a plastic socket that is inserted into the pelvis. The shaft and socket are held in place by acrylic cement. The majority of hip replacements are a result of osteoarthritis, a degenerative joint disease that results in the loss of cartilage between the joint and the growth of bone in place of the cartilage. This causes pain, stiffness and loss of mobility.