Rotator cuff

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Rotator cuff
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Muscles on the dorsum of the scapula, and the Triceps brachii.
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The scapular and circumflex arteries.
Gray's	subject #123

The rotator cuff is an anatomical term given to the group of muscles and their tendons that act to stabilize the shoulder.

1 Function
2 Muscles comprising rotator cuff
3 Injuries
4 Strengthening

[edit] Function

These muscles arise from the scapula and connect to the head of the humerus forming a cuff at shoulder joint. They are important because they hold the head of the humerus in the small and shallow glenoid fossa of the scapula. The glenohumeral joint is often likened to a golf ball sitting on a golf tee. During elevation of the arm, the rotator cuff compresses the glenohumeral joint in order to allow the large deltoid muscle to further elevate the arm. In other words, without the rotator cuff, the humeral head would ride up partially out of the glenoid fossa and the efficiency of the deltoid muscle would be much less.

[edit] Muscles comprising rotator cuff

The four muscles that compose this group are:

Supraspinatus muscle, originating from the supraspinous fossa of the scapula, which abducts the arm.
Infraspinatus muscle, originating from the infraspinous fossa of the scapula, which laterally rotates the arm.
Teres minor muscle, originating in the lateral border of the scapula, which also laterally rotates the arm.
Subscapularis muscle, originating from the subscapular fossa of the scapula, which medially rotates the humerus.

A mnemonic to remember what muscles form the rotator cuff is SITS (supraspinatus, infraspinatus, teres minor, subscapularis) - someone with a rotator cuff injury sits out.

[edit] Injuries

This group of tendons can become torn, leading to pain and restricted movement of the arm. A torn rotator cuff can occur following a trauma to the shoulder or it can occur through "wear and tear" of the tendons under the acromion. It is an injury frequently sustained by athletes whose duties involve making repetitive throws, such as baseball pitchers, American football quarterbacks, or swimmers. It is commonly associated with motions that require repeated overhead motions or forceful pulling motions.

[edit] Strengthening

The rotator cuff can be strengthened to rehabilitate shoulder injuries, and prevent future ones. There are different exercises to target the individual rotator cuff muscles, but the most effective is the side-lying abduction, which activates the supraspinatus, subscapularis and infraspinatus. The side-lying abduction involves the person selecting a dumbbell of low weight initially when first training - four or five kilograms. The lifter lies on a bench sideways, with the arm next to their side and flexed 90 degrees at the elbow. The dumbbell should then be raised towards the ceiling to a 45 degree angle, with the arm still flexed and close to the body, at a pace of two seconds up and four seconds down. The side-lying abduction does not involve the teres minor, but moderately involve the deltoid muscles, making it an excellent all-round shoulder exercise.

Another exercise is the propped external rotator, which targets the infraspinatus and teres minor. The lifter should sit perpendicular to the barbell, with their arm flexed at 90 degrees at the elbow and the forearm resting parallel on the barbell. Again, selecting a dumbbell of modest weight if just beginning, raise the dumbbell up until the forearm points up. Slowly lower the dumbbell and repeat, exercising both arms.

The final exercise is the lateral raise with internal rotation (LRIR). Grasping a dumbbell in both hands, the lifter should internally rotate their arm so that their extended thumbs point towards the floor - as if the lifter is emptying a drink into a bin. The lifter should then raise their arms sideways, with the thumbs still pointing downwards, until the dumbbells are just below the shoulders. The LRIR primarily targets the supraspinatus.

Strengthening the rotator cuff allows for increased loads in a variety of exercises. When lifters plateau on a pushing exercise, such as the bench press or military press, strengthening the rotator cuff can often allow them to break out. It also prevents future injuries to the glenohumeral joint, balancing the often-dominant internal rotators with stronger external rotators. Finally, exercising the rotator cuff can lead to improve posture, as without exercise to the external rotator, the internal rotators can see a shortening, leading to tightness. This often manifests itself as rounded shoulders in the population.

Muscles of the Head — Neck — Trunk — Upper limb — Lower limb— LIST OF ALL MUSCLES