What is the primary action of the supraspinatus?

What is the primary action of the supraspinatus?

• A. Abducts arm first 15 degrees
• B. Adducts arm
• C. Laterally rotates arm
• D. Medially rotates arm

Answer: (A)

The main action of the supraspinatus is to initiate shoulder abduction, especially the first 15 degrees of movement. It sits in the supraspinous fossa and its tendon pulls the humeral head into the glenoid while starting the lift of the arm. After this initial phase, the deltoid becomes the primary abductor for further elevation, with the supraspinatus and other rotator cuff muscles helping to stabilize the joint and keep the head centered. The other actions listed are performed by different muscles: adduction by pectoralis major, latissimus dorsi, and teres major; lateral rotation by infraspinatus and teres minor; medial rotation by subscapularis.

The main action of the supraspinatus is to initiate shoulder abduction, especially the first 15 degrees of movement. It sits in the supraspinous fossa and its tendon pulls the humeral head into the glenoid while starting the lift of the arm. After this initial phase, the deltoid becomes the primary abductor for further elevation, with the supraspinatus and other rotator cuff muscles helping to stabilize the joint and keep the head centered. The other actions listed are performed by different muscles: adduction by pectoralis major, latissimus dorsi, and teres major; lateral rotation by infraspinatus and teres minor; medial rotation by subscapularis.