Subscapularis
Musculus subscapularis
The largest and strongest rotator cuff muscle. It fills the subscapular fossa on the costal surface of the scapula and is the main medial rotator of the humerus.
Overview
Subscapularis is a thick, triangular, multipennate muscle. It arises from the subscapular fossa on the anterior (costal) surface of the scapula and passes in front of the shoulder joint to the lesser tubercle of the humerus. It forms most of the posterior wall of the axilla. Its tendon is separated from the neck of the scapula by the subscapular bursa, which communicates with the joint cavity.
It medially rotates and adducts the arm and is the main anterior dynamic stabiliser of the shoulder, resisting anterior dislocation of the humeral head. It is supplied by the upper and lower subscapular nerves (C5–C6), branches of the posterior cord.
Anatomy
- Origin
Subscapular fossa (most of the anterior surface of the scapula).
- Insertion
Lesser tubercle of the humerus and the anterior joint capsule.
- Action
Medial rotation and adduction of the arm; holds the humeral head in the glenoid.
- Innervation
Upper and lower subscapular nerves (posterior cord).
- Nerve roots
C5–C6 (C7)
- Arterial supply
Subscapular artery; suprascapular and lateral thoracic branches.
- Relations
Lies on serratus anterior, separated by a fascial plane (scapulothoracic space). Forms the posterior wall of the axilla together with teres major and latissimus dorsi.
Function
- Medially rotates the humerus
- Adducts the arm
- Anterior stabiliser of the glenohumeral joint
Clinical significance
Subscapularis tear
Often occurs with anterior dislocation in older patients. Signs are increased passive external rotation, a positive lift-off test (the patient cannot lift the hand off the back) and a positive belly-press test. The tear may also destabilise the long head of biceps tendon.
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.