The supraspinatus contributes to which shoulder action?

• A. Abduct the shoulder
• B. Extend the elbow
• C. Medially rotate the shoulder
• D. Adduct the shoulder

Answer: (A)

Shoulder abduction is the action the supraspinatus primarily initiates. This small rotator cuff muscle sits in the supraspinous fossa and runs under the acromion to the greater tubercle of the humerus. When it contracts, it pulls the humeral head into the glenoid and starts lifting the arm away from the body, especially for the first roughly 15 degrees of movement. After this initial lift, the deltoid takes over to continue the abduction, while the supraspinatus also helps stabilize the joint during the motion.

Elbow extension involves the triceps, not the shoulder joint. Medial rotation is mainly the role of the subscapularis (with supporting input from other rotator cuff and scapular muscles), and adduction is primarily performed by muscles like the pectoralis major, latissimus dorsi, and teres major.