Rotator Cuff Tears – Why Do They Occur?

by D. Christopher Young, MD

What is the rotator cuff? 

The shoulder is a ball (humeral head) and socket (glenoid) joint.  These two bones come together and form the shoulder joint.  Articular cartilage covers the surfaces of the ball and socket, creating smooth surfaces with minimal friction. There are 4 muscle/tendon units coming from the shoulder blade and surround the shoulder joint in the front, on the top and in the back.   These four muscle/tendon units that envelop the shoulder are called the “rotator cuff.”   The rotator cuff contains the control and controls many shoulder motions.  When one of these tendons is inflamed, this is called tendonitis.  If one or more of these tendons detaches from the bone, this is called a rotator cuff tear.  One of the tendons is called the supraspinatus tendon.  It runs over the top of the shoulder and helps elevate the arm.  The supraspinatus is the most commonly injured part of the rotator cuff.

How do tears of the rotator cuff occur?

Tears of the rotator cuff can be due to traumatic or atraumatic causes (or a combination of both).  They are diagnosed by a combination of history, physical exam, x-rays and ultimately an MRI.

Traumatic tears are usually the result of a fall.  The average age of rotator cuff tears that we operate on is 59.  Usually, there is immediate pain and a feeling of weakness.  Some people have the inability to lift their arm overhead, although this is usually temporary, as other muscles learn to compensate.  Traumatic tears usually need surgery.

Atraumatic tears are multifactorial in causation. These factors include genetic predisposition, natural attrition of the tendon, old trauma, overuse, high demand occupations and sometimes bad luck.  These tears can occur silently over time but may become painful.  Initial treatment of these tears is usually non-operative, although there is some controversy on this point.  Nonoperative measures include anti-inflammatory pills, cortisone shots, physical therapy, etc.  There are some newer measures such as PRP and stem cells which may be considered as well.  If someone responds well to nonoperative management, they should still be followed as the tears can progress.  Surgery is indicated when conservative measures fail. 

Of course, rotator cuff tears can be a combination of the above so management must be individualized.
For more information, current evidence-based guidelines are available from the American Association of Orthopaedic Surgeons.