Coloured profile X-rays of the left knee of a female 68-year-old patient with osteoarthritis before (left) and after (right) a total knee replacement. Knee replacement is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve pain and disability. Osteoarthritis (or arthrosis) is a common degenerative disease characterised by a loss of the cartilage that lines the joints between bones. This leads to pain, swelling and occasionally may result in the loss of function of the affected joint.