Arthritis involves the wearing down of the cartilage (smooth bearing surface) of a joint. This may be a result of an old injury, an inflammatory condition, or simple wear and tear. In the shoulder, this is sometimes caused by a longstanding dysfunction from a chronically torn rotator cuff tendon. Treatment of arthritis in the shoulder may include injections of steroids, physical therapy, and medication. When conservative treatment has failed, your surgeon may recommend a shoulder replacement. Depending on the cause of arthritis, this may be a standard shoulder replacement or a reverse shoulder replacement (which removes the need for a rotator cuff).