Knee joint replacement. Coloured X-ray of the knee of a 56 year old man (front view) showing an artificial (prosthetic) joint replacing the knee joint. The entire knee joint surface has been replaced here. The implant (white) made of metal alloy attaches to the bottom of the femur (thigh bone, upper frame) and to the top of the tibia (shin bone, lower frame). It forms a flexible joint that can hinge like the old joint, relieving joint pain and immobility. Following surgery, metal sutures (blue) are seen on the skin surface and a catheter draining the area is visible. Knee joint replacement is conducted usually because of joint disease such as osteoarthritis or due to injury.