Which muscle medially rotates the shoulder?

Which muscle medially rotates the shoulder?

• A. Subscapularis
• B. Infraspinatus
• C. Supraspinatus
• D. Teres Minor

Answer: (A)

Medial rotation of the shoulder (internal rotation) is produced by a muscle that lies on the anterior surface of the scapula and attaches to the humerus to pull it inward. Subscapularis fits this role precisely: it inserts on the lesser tubercle of the humerus and, when it contracts, draws the humeral head medially, rotating the arm inward and helping stabilize the joint as part of the rotator cuff. The other muscles listed act differently: infraspinatus and teres minor are external rotators, rotating the arm outward. Supraspinatus mainly initiates arm abduction rather than rotation.

Medial rotation of the shoulder (internal rotation) is produced by a muscle that lies on the anterior surface of the scapula and attaches to the humerus to pull it inward. Subscapularis fits this role precisely: it inserts on the lesser tubercle of the humerus and, when it contracts, draws the humeral head medially, rotating the arm inward and helping stabilize the joint as part of the rotator cuff.

The other muscles listed act differently: infraspinatus and teres minor are external rotators, rotating the arm outward. Supraspinatus mainly initiates arm abduction rather than rotation.