What Are the Four Muscles of the Rotator Cuff?

The rotator cuff is a group of four muscles that combine at the shoulder. The four individual muscles keep the shoulder joint stable. These muscles control elevating and rotating the arm. The names of the four muscles are the supraspinatus, infraspinatus, teres minor and subscapularis. The mnemonic way of recalling the four muscles is "SITS."

Supraspinatus

The supraspinatus elevates the shoulder joint and works with the other muscles to keep the head of the humerus bone stable within the shoulder joint. The supraspinatus muscle resists the gravitational pull on the shoulder created by the weight of the arm. This muscle is the most commonly injured of the four rotator cuff muscles according to Exercise Prescription on the Net (see Referenes section), an informational website for exercise professionals, coaches and fitness enthusiasts.

Infraspinatus

The infraspinatus, along with the teres minor, controls external rotation of the shoulder. It carries the arm backward. The infraspinatus also helps keep the humerus bone stabilized in the shoulder joint. This muscle is the second most frequently injured of the four rotator cuff muscles.

Teres Minor

The teres minor, along with the infraspinatus, acts to rotate the arm in an outward manner. It works with the other rotator cuff muscles to keep the shoulder joint stable. The term "teres" means smooth and round in Latin. It is easily fatigued and can sometimes cause pain in the third and fourth fingers.

Subscapularis

The subscapularis controls the internal rotation of the head of the humerus. It brings the humerus forward and down when the arm is raised. The subscapularis provides strong protection to the front of the shoulder joint and prevents displacement.

Injury/Treatment

The muscles of the rotator cuff provide the greatest range of motion of any joint of the body. Injuries can be caused by falling, lifting or making repetitive arm motions, especially those that are done overhead. Shoulder pain that lasts more than two days or prohibits your ability to work should be examined by a doctor. Apply ice for 15 to 20 minutes, three times a day for two days. After two days, apply heat. Take ibuprofen or naproxen for discomfort.