What parts of the shoulder are affected?
The shoulder is made up of the bones of the shoulder blade (scapula), the upper arm (humerus) and the collarbone (clavicle). They are surrounded by a bundle of muscle tendons called the rotator cuff. This cuff connects the humerus to the scapula allowing movement of the arm at the shoulder joint and keeping the humerus tightly hold in the socket of the shoulder (glenoid). As this glenoid is very shallow and flat, there is a rim of soft tissue (labrum) surrounding its edge, and making the socket more like a cup. This way, the socket fits the head of the humerus better. All these structures are covered by a joint capsule made of ligaments, which holds fluids to lubricate the joint. This capsule is somewhat loose so that the shoulder can move freely. If the shoulder moves too far from the original position, though, the ligaments in the capsule become tight and stop it from going to far. When a force –either external, like running into a fielder; or internal, like pitching an extremely fas
