Hip replacement surgery. Surgeon (right) using a surgical tool to gouge out bone from a patient's pelvis during hip replacement surgery. This will form a space around the old hip socket for the insertion of an artificial hip socket. This will connect to a ball-and-pin implant placed in the shaft of the femur (upper leg bone) to replace the old femoral head, forming a new hip joint. This surgery is usually 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.