Arthroplasty

The wrist is a more complicated joint than the hip or the knee. At the base of the hand are two rows of bones, with four bones in each row. These are called the carpals. The long thin bones of the hand radiate out from one row of carpals toward the fingers and thumb. The two bones of the lower arm (radius and ulna) form a joint with the other row of carpals. All the bone ends are covered with a slick, elastic tissue called cartilage, which enables the bones to move smoothly against each other. However, if the cartilage is worn away or damaged by injury, infection or disease, the bones will rub against each other causing pain. During any total joint replacement, the worn-out bone ends are removed and replaced by an artificial joint (prosthesis).