The shoulder has a wider and more varied range of motion than any other joint in your body. Your shoulder allows you to do everything from painting the house to playing basketball, but this flexibility also makes the shoulder one of the most unstable joints in the body.
In fact, the shoulder is not a single joint. It is a complex arrangement of bones, ligaments, muscles, and tendons that is better referred to by the term shoulder girdle. The primary function of the shoulder girdle is to give strength and range of motion to the arm. The shoulder girdle includes three bones: the scapula, clavicle and humerus. It also has three joints: glenohumeral, acromioclavicular, and sternoclavicular.
ORTHOPAEDIC SERVICES FOR THE SHOULDER