Which muscle abducts the shoulder?

Which muscle abducts the shoulder?

• A. Teres Major
• B. Subscapularis
• C. Biceps Brachii
• D. Supraspinatus

Answer: (D)

Abduction of the shoulder begins with the supraspinatus. This muscle sits in the supraspinous fossa of the scapula and inserts on the greater tubercle of the humerus, pulling the humeral head into the glenoid as the arm starts to lift. That initial 0 to roughly 15 degrees of elevation is mainly produced by the supraspinatus, and it also helps stabilize the joint during movement. After this early phase, the deltoid becomes the primary mover for lifting the arm further. The other muscles listed don’t abduct the shoulder as their main action: subscapularis medially rotates and stabilizes the joint, teres major adducts and medially rotates, and the biceps brachii primarily flexes the elbow (with a role in forearm supination, and only a secondary assist in shoulder movements).

Abduction of the shoulder begins with the supraspinatus. This muscle sits in the supraspinous fossa of the scapula and inserts on the greater tubercle of the humerus, pulling the humeral head into the glenoid as the arm starts to lift. That initial 0 to roughly 15 degrees of elevation is mainly produced by the supraspinatus, and it also helps stabilize the joint during movement. After this early phase, the deltoid becomes the primary mover for lifting the arm further. The other muscles listed don’t abduct the shoulder as their main action: subscapularis medially rotates and stabilizes the joint, teres major adducts and medially rotates, and the biceps brachii primarily flexes the elbow (with a role in forearm supination, and only a secondary assist in shoulder movements).