College of Massage Therapists of British Columbia (CMTBC) Practice Exam

Which muscle's shortness contributes to internal rotation of the glenohumeral joint?

1. Teres minor

2. Infraspinatus

3. Subscapularis

4. Pectoralis minor

The correct answer is: Subscapularis

The subscapularis muscle is a key contributor to the internal rotation of the glenohumeral joint. This muscle is one of the four rotator cuff muscles, located on the anterior surface of the scapula. When the subscapularis contracts, it pulls the humerus toward the front of the body, effectively rotating it inward. This action occurs due to the muscle's orientation and attachment points, which facilitate internal rotation. In contrast, other muscles such as teres minor and infraspinatus primarily facilitate external rotation of the shoulder. Pectoralis minor, while involved in movements of the scapula, does not play a direct role in the internal rotation of the humerus at the glenohumeral joint. Therefore, the shortness of the subscapularis contributes directly to internal rotation, making it the correct answer.