Various prosthetic procedures are used to treat osteoarthritis of the shoulder today. Total shoulder replacement of the ball and socket joint is now only performed in younger patients whose soft tissue (rotator cuff) is in good condition. Nowadays, these implants are designed in such a way that they could later be converted into a reverse shoulder replacement if required. Hemiarthroplasty, or replacement of the humeral head (ball) but not the acetabular cup (socket), used to be performed frequently but is now only rarely indicated; it is used primarily in comminuted fracture (when the bone is broken into more than two fragments). In older patients who may have some wear or injury to the rotator cuff, primary reverse shoulder replacement is increasingly being recommended today. Cup arthroplasty, which involves replacement of the surface of the humeral head only, has both supporters and opponents. Its supporters argue that it provides optimal treatment of osteoarthritis of the shoulder and that a rotator cuff rupture can also be easily repaired, but the acetabular cup does not have to be replaced. In addition, hardly any of the patient’s own bone has to be sacrificed, leaving all options still open for the patient in the future. Opponents argue that if it becomes necessary to use an acetabular component in the future, the surgery and the insertion of the acetabular cup would be very difficult, which is why they recommend primary total shoulder replacement of both the humeral head and the acetabulum.