As you move your arm, the ball-shaped end of the upper arm, or humerus, moves against a cup-like depression in shoulder bone, or scapula.
As long as the upper arm can slide against the shoulder, you are able to move your arm comfortably. But over time, especially in patients who suffer from arthritis, the shoulder joint can wear down.
Cartilage, the tissue that cushions the bones and makes it possible for them to move smoothly against each other can wear away. When this happens, the bones run together, causing pain and restricting arm movement.
No matter what the cause, one of the most effective ways to fix a damaged shoulder is to replace it surgically. In this procedure, the ball-shaped bone at the top of the upper arm is removed and replaced with a metal substitute.
The shoulder socket is widened and lined with a smooth pad that allows the metal ball joint to move more freely against the shoulder blade. Shoulder replacement surgery is a major operation, but your doctor believes that the procedure -- followed up with physical therapy and time to heal -- will result in reduced pain and greater mobility.