Total hip replacement. Coloured X-ray of the pelvis of an 86 year old woman, showing a hip replacement (left) and a hip affected by osteoarthritis (right). The replacement hip consists of a ball and shaft (green), embedded in the femur (thigh bone). The ball can move freely in its prosthetic socket (brown) in the pelvis. This provides relief from osteoarthritis, which can be seen in the other hip joint at right. In a healthy individual there is usually a clear space between the ball and socket, but this joint shows little or no space. This is because osteoarthritis results in the loss of cartilage between the joints and the healing process leads to the growth of bone in place of the cartilage, causing pain, stiffness and loss of mobility.