Joint replacement involves surgery to replace the ends of bones in a damaged joint. This surgery creates new joint surfaces. In shoulder replacement surgery, doctors replace the ends of the damaged upper arm bone (humerus) and usually the shoulder bone (scapula) or cap them with artificial surfaces lined with plastic or metal and plastic. Shoulder joint components may be held in place with cement. Or they may be made with material that allows new bone to grow into the joint component over time to hold it in place without cement. The top end of your upper arm bone is shaped like a ball. Muscles and ligaments hold this ball against a cup-shaped part of the shoulder bone. Surgeons usually replace the top of the upper arm bone with a long metal piece, inserted into your upper arm bone, that has a rounded head. If the cup-shaped surface of your shoulder bone that cradles your upper arm bone is also damaged, doctors smooth it and then cap it with a plastic or metal and plastic piece. Surgeons are now trying a newer procedure called a reverse total shoulder replacement for people who have painful arthritis in their shoulder and also have damage to the muscles around the shoulder. In this procedure, after the surgeon removes the damaged bone and smooths the ends, he or she attaches the rounded joint piece to the shoulder bone and uses the cup-shaped piece to replace the top of the upper arm bone. Early results are encouraging.1 This surgery is not right for everyone. And not all surgeons have done it. Success depends not only on careful evaluation to be sure it's the right surgery for you but also on having a surgeon with experience in reverse shoulder replacement.