Hip replacement surgery. Image 20 of 30. Surgeon cleaning up during hip replacement surgery. The operation is nearly finished. The ball (metallic) of the femoral implant has been inserted into the socket (white) implanted into the pelvis. This has formed the new hip joint to replace the old one, which was surgically removed. This surgery is usually performed in response to arthritis, degeneration of the joints, and restores mobility to people who would otherwise be incapacitated by pain and unable to move freely. For a sequence of images showing the full surgery, see M551/340-369. For a sequence showing the operation on the femur, see images M551/344-359.