If the cartilage is damaged by injury or worn away by, for example arthritis, the ends of the bones can rub together, causing pain and restricting movement.

The operation involves removing the damaged surfaces of the knee and replacing them with an artificial joint containing metal and plastic component. For vast majority of people, it is an extremely successful operation.

The aim is to replace a knee joint that is painful, stiff and often deformed with the one that is pain-free, moves easily and is correctly aligned.