 The majority of shoulder function comes from the interactions of the glenohumeral ligament complex, the rotator cuff complex, and the articulating bones. The superior glenohumeral ligament is important in stabilization of the glenohumeral joint in adduction and external rotation. The middle glenohumeral ligament is an important stabilizing structure in the positions of adduction and external rotation and abduction up to 45 in external rotation. The resistance, and therefore tension, of the inferior glenohumeral ligament, which is negligible in positions of neutral adduction and adduction in external rotation, increases in value for angles between 45 and 90, indicating the important stabilizing function of this ligament in those positions. The rotator cuff is comprised of the tendons of the supraspinatus, infraspinatus, teres minor, and subscapularis muscles1,10. 