The subscapularis begins on the anterior scapular, or subscapular fossa, and introduces onto the minor tuberosity of the humerus. It is the largest of the rotator cuff muscles and its cross-sectional area is larger than the other three rotator cuff muscles combined; the infraspinatus, the teres minor and the supraspinatus. The most essential functions of the glenohumeral joint are: depressor of the humeral head; anterior stabilizer of the humeral head, which means it glides the humeral head posteriorly relative to the glenoid fossa; and internal rotator of the shoulder together with the powerful pectoralis major and latissimus dorsi.
The tendon fibres combine with the anterior capsule of the shoulder, which serve to reinforce the anterior shoulder capsule. The muscle is considered to be less substantial as a shoulder internal rotator, as the pectoralis major and latissimus dorsi are powerful internal rotators, and it’s therefore more essential as a dynamic anterior stabilizer of the glenohumeral joint due to its action in preventing an anterior shear of the humeral head.
The subscapularis has a deep connection with the long head of the biceps. This is known as a capsuloligamentous complex that functions to stabilize the long head of the biceps tendon in the bicipital groove. The pulley complex is made up of the superior glenohumeral ligament, the coracohumeral ligament, and the distal attachment of the subscapularis tendon, where it is located within the rotator interval between the anterior edge of the supraspinatus tendon and the superior edge of the subscapularis tendon. Subscapularis tendon injuries may weaken the stability of the bicep. In order to maintain the biceps tendon stabilized and in place, support of the most superior insertion point of the subscapularis from behind the ligament and tension in the superior glenohumeral ligament is needed. Issues with a biceps sling is a common cause and effect of disease in many athletes, requiring the constant and effective rotation of the shoulder, just like the cocking position during baseball pitching.
Shoulder pain is common among many athletes, however, subscapularis muscle injuries, although infrequent, can occasionally occur, causing complications. Direct trauma from an injury to this specific muscle-tendon structure can commonly affect overhead athletes, such as tennis players and swimmers. For more information, please feel free to ask Dr. Jimenez or contact us at (915) 850-0900.