X-ray the pelvis of a 72 year old male patient showing osteoarthritis of the right hip (left). The patient had previously fractured the hip. The ball at the top of the femur (thigh bone) fits into the socket of the hip. In a healthy individual there is usually a clear space between the ball and socket, but these joints show little or no space. Osteoarthritis results in the loss of cartilage between the joint. The healing process leads to the growth of bone in place of the cartilage, causing pain, stiffness and loss of mobility. Treatment is with the surgical replacement of the joint.