Shoulder pain is a common musculoskeletal complaint that may be due either to intrinsic disorders of the shoulder or referred pain. The former include injuries and acute or chronic inflammation of the shoulder joint, tendons, surrounding ligaments, or periarticular structures.
A complex network of anatomic structures endows the human shoulder with tremendous mobility, greater than any other joint in the body. The shoulder girdle is composed of three bones (the clavicle, scapula, and proximal humerus) and four articular surfaces (sternoclavicular, acromioclavicular, glenohumeral, and scapulothoracic) (figure 1A-C). The glenohumeral joint, commonly referred to as the shoulder joint, is the principal articulation.