(1) It is the most complex and most mobile part of the body.
(2) It consists of 4 articulations---the glenohumeral joint (top of the arm connects at the shoulder), the sternoclavicular joint (the collarbone connects near the throat), the acromioclavicular joint (outer end of the collarbone connects with a bony projection off the shoulderblade, and the scapulothoracic articulation (the scapula, or shoulderblade, contacts the rear chest wall).
(3) Pain in the shoulder may not be a shoulder problem, but be referred pain from 3 common sites---the heart, the lungs, and the neck.
(4) Shoulder dislocation involving the humerus (bone in the upper arm) is common because of the shallowness of the “cup” holding the humeral head.
(5) Bursitis is common in the shoulder, caused by inflammation due to repetitive motions (e.g. painting, drywalling, throwing sports).
