Rotator Cuff Tear

The rotator cuff is key to the healthy functioning of the shoulder. The rotator cuff tendons are subject to impingement and injury. Tearing a rotator cuff tendon is an especially painful injury. A torn rotator cuff creates a very weak shoulder.

A torn rotator cuff is a common injury in middle-aged people. It is usually associated with impingement (pinching) of the rotator cuff tendons. It can also be the result of a sports injury. Athletes with torn rotator cuffs frequently use overhand motions, such as baseball pitchers. But even doing routine chores like cleaning windows, waxing cars, or painting can lead to a rotator cuff tear.

Anatomy of the Shoulder

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 separate muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles raise and rotate the arm by pulling on the tendons. As the arm is raised, the rotator cuff keeps the humerus bone tightly in the socket of the scapula. The acromion and coracoid process are both protrusions of the scapula bone.

A bursa is located between the acromion process and the rotator cuff tendons. This bursa is a lubricated sac of tissue that cuts down on the friction between the acromion and the rotator cuff. Bursae are located in many joints of the body, where tissues rub against each other. In this case, the bursa protects the acromion and the rotator cuff from grinding against each other.

What Causes a Rotator Cuff to Tear?

A rotator cuff tear is often the end stage of impingement by a subacromial bone spur. The supraspinatus tendon is especially prone to this. The impingement can damage the bursa (a common cause of shoulder bursitis) and eventually erode the rotator cuff tendons. A torn rotator cuff can also be caused by degeneration or traumatic injury.

The rotator cuff tendons have areas of very low blood supply. The more blood supply a tissue has, the better and faster it can repair and maintain itself. The areas of poor blood supply in the rotator cuff make these tendons especially vulnerable to degeneration. The degeneration caused by repetitive shoulder motions helps explain why the rotator cuff tear is such a common sports injury. Rotator cuff tears usually occur in areas of the tendon that had low blood supply to begin with and then were further weakened by degeneration.

Excessive force can tear weak rotator cuff tendons. This force can come from trying to catch a heavy falling object or lifting an extremely heavy weight with the arm extended. The force can also be from a fall directly onto the shoulder. Sometimes injuries that tear the rotator cuff are painful, but sometimes they aren't. Researchers estimate that up to 40 percent of athletes may have a mild rotator cuff tear without even knowing it.

The typical patient with a rotator cuff tear has had problems with the shoulder for some time. This patient has overextended the shoulder and torn one or more rotator cuff tendons. In some cases, a rotator cuff may tear only partially. In other cases, the tendons are completely ruptured, and the patient is unable to raise the arm.