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I tore my rotator cuff in a motorcycle accident. Just the subscapularis tendon was torn. That's the only injury I had. The doc said something about that being an uncommon injury. What can you tell me about it?

The shoulder is made up of three bones: the scapula (shoulder blade), the humerus (upper arm bone), and the clavicle (collarbone). The rotator cuff connects the humerus to the scapula. The rotator cuff is formed by the tendons of four muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis. The rotator cuff helps raise and rotate the arm. Rotator cuff tears cause pain and weakness in the affected shoulder. In some cases, a rotator cuff may tear only partially. The shoulder may be painful, but you can still move the arm in a normal range of motion. In general, the larger the tear, the more weakness it causes. In other cases, the rotator cuff tendons completely rupture. A complete tear makes it impossible to move the arm in a normal range of motion. It is usually impossible to raise the arm away from your side by yourself. The largest muscle in the rotator cuff is the subscapularis. This muscle helps rotate the shoulder and arm inward (internal rotation). The subscapularis helps stabilize the shoulder in the socket and prevent forceful anterior (forward) dislocations. The subscapularis also helps balance the force applied on the shoulder from the posterior (back side of the) rotator cuff. The rotator cuff surrounds the entire shoulder joint like an envelope (front, back, side, and under the arm). Any weakness on one side from a tear or damage to the rotator cuff will affect how the rest of the cuff functions. It is unusual to have an isolated subscapularis tendon tear. If the trauma or force is strong enough to rupture this portion of the rotator cuff then it's likely other areas have been damaged. This could include other rotator cuff tendons, ligaments, and/or the joint surface. Other muscle/tendon units around the shoulder that are not part of the rotator cuff can also be injured (e.g., biceps tendon).

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