The subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint. Structure It arises from its medial two-thirds and from the lower two-thirds of the groove on the axillary border (subscapular fossa) of the scapula. Some fibers arise from tendinous laminae, which intersect the muscle and are attached to ridges on the bone; others from an aponeurosis, which separates the muscle from the teres major and the long head of the triceps brachii. The fibers pass laterally and coalesce into a tendon that is inserted into the lesser tubercle of the humerus and the anterior part of the shoulder-joint capsule. Tendinous fibers extend to the greater tubercle with insertions into the bicipital groove. Relations The tendon of the muscle is separated from the neck of the scapula by a large bursa, which communicates with the cavity of the shoulder-joint through an aperture in the capsule. The subscapularis is separated from the serratus anterior by the subscapularis (supraserratus) bursa. Nerve supply The subscapularis is supplied by the upper and lower subscapular nerves, branches of the posterior cord of the brachial plexus. (C5-C6) Function The subscapularis rotates the head of the humerus medially (internal rotation) and adducts it; when the arm is raised, it draws the humerus forward and downward. It is a powerful defense to the front of the shoulder-joint, preventing displacement of the head of the humerus. Clinical significance Examination The Gerber Lift-off test is the established clinical test for examination of the subscapularis. The bear hug test (internal rotation while palm is held on opposite shoulder and elbow is held in a position of maximal anterior translation) for subscapularis muscle tears has high sensitivity. Positive bear-hug and belly press tests indicate significant tearing of subscapularis. Imaging There is no singularly imaging device or technique for a satisfying and complete subscapularis examination, but rather the combination of the sagittal oblique MRI / short-axis US and axial MRI / long-axis US planes seems to generate useful results. Additionally, lesser tuberosity bony changes have been associated with subscapularis tendon tears. Findings with cysts seem to be more specific and combined findings with cortical irregularities more sensitive. Another fact typically for the subscapularis muscle is the fatty infiltration of the superior portions, while sparing the inferior portions. Since the long biceps tendon absents itself