Which muscle is NOT part of the rotator cuff?

Which muscle is NOT part of the rotator cuff?

• A. Supraspinatus
• B. Infraspinatus
• C. Subscapularis
• D. Deltoid

Answer: (D)

The rotator cuff is a set of four muscles that stabilize the shoulder by keeping the head of the humerus centered in the glenoid socket. Those four muscles are the supraspinatus, infraspinatus, teres minor, and subscapularis. The deltoid does not belong to this group. The deltoid is the large, outer shoulder muscle responsible for lifting the arm and giving the shoulder its rounded contour. It inserts on the deltoid tuberosity of the humerus and works to abduct the arm after the initial movement. In contrast, the rotator cuff muscles provide joint stability and precise rotations: supraspinatus initiates abduction, while infraspinatus and teres minor externally rotate, and subscapularis internally rotates the arm.

The rotator cuff is a set of four muscles that stabilize the shoulder by keeping the head of the humerus centered in the glenoid socket. Those four muscles are the supraspinatus, infraspinatus, teres minor, and subscapularis. The deltoid does not belong to this group.

The deltoid is the large, outer shoulder muscle responsible for lifting the arm and giving the shoulder its rounded contour. It inserts on the deltoid tuberosity of the humerus and works to abduct the arm after the initial movement. In contrast, the rotator cuff muscles provide joint stability and precise rotations: supraspinatus initiates abduction, while infraspinatus and teres minor externally rotate, and subscapularis internally rotates the arm.