Hip replacement surgery. Surgeon (left) using a hammer to insert an implant into a patient's feumr (upper leg bone) during hip replacement surgery. The head of the femur has already been removed, and space was made in the femoral shaft to contain this artificial shaft (top bit just seen at lower right) that will support a ball to replace the femoral head. This will connect to an artificial socket that replaces the old pelvic socket. These implants will connect to form the new hip joint. This surgery is mostly performed due to arthritis, the degeneration of the joints, and restores mobility to people who would otherwise be incapacitated by pain and unable to move freely.