Which rotator cuff muscle primarily abducts the arm?

Which rotator cuff muscle primarily abducts the arm?

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

Answer: (C)

Supraspinatus is the muscle that initiates and primarily abducts the arm. It sits in the supraspinous fossa, passes under the acromion, and attaches to the superior part of the greater tubercle of the humerus. As you begin to lift the arm, this tendon pulls the humeral head into the glenoid and generates the initial upward movement for the first roughly 15 degrees of abduction. After that initial phase, the deltoid becomes the main mover for further elevation, while the supraspinatus continues to help stabilize the joint and assist with ongoing abduction. The other rotator cuff muscles—infraspinatus and teres minor, which mainly external rotate and help with stabilization, and subscapularis, which mainly internal rotates and stabilizes—do not primarily drive abduction.

Supraspinatus is the muscle that initiates and primarily abducts the arm. It sits in the supraspinous fossa, passes under the acromion, and attaches to the superior part of the greater tubercle of the humerus. As you begin to lift the arm, this tendon pulls the humeral head into the glenoid and generates the initial upward movement for the first roughly 15 degrees of abduction. After that initial phase, the deltoid becomes the main mover for further elevation, while the supraspinatus continues to help stabilize the joint and assist with ongoing abduction. The other rotator cuff muscles—infraspinatus and teres minor, which mainly external rotate and help with stabilization, and subscapularis, which mainly internal rotates and stabilizes—do not primarily drive abduction.