The shoulder is a ball (humeral head) and socket (glenoid) joint, and it is the most mobile joint in the body. However, the socket (glenoid) is shallow, covering less than half of the ball (humeral head) and provides little stability.
The shoulder joint is held in place by muscles and bands of connective tissue called tendons and ligaments. Four major muscles (subscapularis, supraspinatus, infraspinatus and teres minor) and their tendons connect the upper arm bone (humerus) with the shoulder blade (scapula).
There are many different types of shoulder injuries and tears; however, there are a few that are more common than others. Common types of injuries are rotator cuff tears, biceps tendon rupture, Bankart Lesion, and Superior Labrum from Anterior to Posterior (SLAP) lesions.
Many of these injuries can occur from long-term overuse, such as repetitive lifting, pushing, pulling and throwing. For this reason, athletes and skilled workers are particularly prone to shoulder injuries.