Massage Today
August, 2004, Vol. 04, Issue 08

The Most Common Shoulder Injury

By Ben Benjamin, PhD

Question: Which is the strongest rotator cuff muscle?

Answer: The subscapularis muscle.

The subscapularis muscle is, mechanically, the best situated of all the rotator cuff muscles.

It is not only the strongest of the four rotator cuff muscles, but also the muscle most frequently used. In most individuals, the subscapularis is at least two-to-three times stronger than the supraspinatusinfraspinatus muscles, and 5-to-10 times stronger than the smaller, weaker teres minor muscle. The subscapularis is the muscle we use for forehand strokes in racquet sports, as well as for a tennis serve. It is one of the primary muscles used in swimming, hitting or throwing a ball. When the subscapularis is injured, we have trouble getting dressed or lying on our side to go to sleep.

True or False? If pain is felt on resisted medial rotation of the arm, the subscapularis tendon is likely to be injured.

Answer: True. Medial rotation is the primary action of the subscapularis muscle-tendon unit (see image at left). When pain is felt during this action, injury to the subscapularis tendon is the usual cause. The muscle belly is broadly attached in the subscapular fossa and is rarely injured.

True or False? If the resisted test for subscapularis tendinitis is negative when performed in the standard 90-degree angle position, laterally rotating the arm to the 180-degree angle will increase the stress on the muscle-tendon unit and often tests positive.

Answer: True. When you wish to increase the stress on any muscle-tendon unit, beginning the anatomical testing procedure with the muscle in a stretched position removes its mechanical advantage and increases the stress placed on the structure.

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