The shoulder joint includes several separate joints - these joints connect the upper extremity and the thorax. The major bones include: the scapula, the humerus, the clavicle and the sternum.
The ligaments, tendons and muscles are combined to maintain shoulder structure and function. The ligaments connect the clavicle and the coracoid process. Shoulder muscles contain multiple layers. Rotator cuff refers to the deep layer muscles, which includes supraspinatus, infraspinatus, teres and subscapularis.
Shoulder joint injuries are common, especially in the following sport activities: tennis, golf, swimming, football and baseball. These sports tend to overuse the shoulder joint. In addition, these sports also cause various traumatic injuries.