ility does enhance range of motion, any dynamic activity involving the arm encountering resistance requires that the head of the humerus remain in contact with the glenoid fossa. This connection is maintained by the joint capsule, the glenohumeral ligaments, and the coordinated action of several different muscles (10:11). The capsule surrounds the joint, being attached to both the glenoid fossa and the neck of the humerus. In general, it is loose fitting and relatively thin. Its overall strength is derived in part from attachment of the rotatory cuff muscle tendons. These include the supraspinatus muscle tendon superiorly, the subscapularis muscle tendon anteriorly, and the teres minor and infraspinatus muscle tendons posteriorly inferiorly, the capsule is less well protected (10:8 9). Each of these tendons blends with the joint capsule to provide it with active, truly dynamic, support and stability. The muscles of the shoulder can be roughly divided into those that primarily move and those that primarily stabilize the complex (12:18). The larger shoulder muscles serve as the main movers. These include the pectoralis major, latissimus dorsi, and the deltoid. The smaller muscles act to stabilize. To a certain extent, the muscles of the rotator cuff serve both functions.
The four rotator cuff muscles all originate from the scapula (6:130). After blending with the shoulder capsule, their tendons subsequently insert into the humeral tuberosities: the subscapularis muscle inserts into the lesser tuberosity and the supraspinatus, infraspinatus, and teres minor muscles all insert into the greater tuberosity (15:123). In a unique arrangement, the four tendons also interlace as they pass over the head of the humerus. This close association allows a functional interaction; all four muscles share can potentially contribute to all glenohumeral joint movements.
As stabilizers, the main function of the rotator cu...