Knee replacement surgery. Surgeon suturing the incision after completing a total knee replacement operation. In this operation the kneecap is moved aside to expose the knee joint. The ends of the tibia (shinbone) and femur (thigh bone) are shaped and fitted with artificial components. The component fixed to the end of the femur is aligned with the component fixed to the end of the 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.