Knee replacement surgery. Surgeon removing excess orthopaedic cement after fitting a prosthetic joint component onto the end of the thigh bone (femur) during a total knee replacement operation. Orthopaedic cement is a putty-like substance which is a type of acrylic glass. It is used to bond joint replacements to existing bone in orthopaedic surgery. In total knee replacement surgery the kneecap is moved aside to expose the knee joint, and the ends of the femur and tibia (shinbone) are shaped to fit prosthetic components. The component fixed to the end of the femur is aligned with the component fixed to the end of the shinbone (tibia), forming an artificial knee joint. Knee joints need replacing when the protective cartilage that lines them is lost. Cartilage can be lost due to injury or arthritis. See clips K004 6229 - K004 6255 for entire sequence.