Muscles medially rotating the arm at the shoulder joint

Subscapularis

Teres major

Latissimus dorsi

Pectoralis major

Deltoid(anterior fibres)

Subscapularis

Subscapularis forms the greater part of the posterior wall of the axilla and as such lies in close proximity to teres major and latissimus dorsi. The anterior surface of the muscle lies on serratus anterior. When seen from the front it forms the upper boundary of the upper triangular and quadrilateral spaces.

Subscapularis is a multipennate muscle which arises from the medial two-thirds of the subscapular fossa and from tendinous septa, which reinforce the muscle, attached to bony ridges in the fossa. There is also an attachment to the fascia covering the muscle. The muscle fibres narrow and form a broad, thick tendon which attaches to the lesser tubercle of the humerus, the capsule of the shoulder joint and the front of the humerus below the tuberosity. A bursa, which communicates directly with the shoulder joint, separates the tendon from the neck of the scapula. 

Nerve supply

Subscapularis is supplied by the upper and lower subscapular nerves, root value C5, 6 and 7, from the posterior cord of the brachial plexus.

Action

Subscapularis is a strong medial rotator of the arm at the shoulder joint; it may also assist in adduction of the arm.

Functional activity

As part of the “rotator cuff”, subscapularis plays an important role in maintaining the integrity of the shoulder joint during movement, by keeping the head of the humerus within the glenoid fossa. It also resists upward displacement of the humeral head when deltoid, biceps and the long head of triceps are active.

Palpation

The muscle belly cannot be palpated as it lies deep to the scapula. However, careful deep palpation may allow the tendon to be felt just before its insertion onto the lesser tuberosity.