Shoulder Impingement

Anatomy

The rotator cuff is made up of four muscles (supraspinatus, infraspinatus, teres minor and subscapularis) that provide strength, stability and a wide range of motion to the shoulder.

The subacromial bursa is a sac that covers and protects the rotator cuff and allows the rotator cuff tendons to glide freely beneath the acromion.  The acromion is an arch of bone that extends from the scapula (or shoulder blade) over the top of the shoulder.  The space between the acromion and the underlying bursa and rotator cuff narrows when the arm is raised.  Shoulder impingement refers to pinching of the bursa and rotator cuff tendons against the acromion, a process that can result in pain and inflammation (see subacromial bursitis) and, ultimately, damage to the rotator cuff tendons.

Mechanical pressures become increased on the rotator cuff due to this impingement process.  Circulation to the affected rotator cuff tendons decrease and these tendons may begin to fray.  Over time, a rotator cuff tear may result (see rotator cuff injuries).

Symptoms

Shoulder impingement can produce pain in the front or side of the shoulder.  This may be increased with overhead lifting or reaching or with direct pressure on the shoulder.  If left untreated, the problem may result in weakness over time.

Diagnosis

Diagnosis requires a thorough history and physical examination to help identify the problem and to exclude other potential causes of shoulder pain.  Pain with rapid passive forward elevation of the shoulder, called an impingement sign, helps to make the diagnosis.  X-ray examination of the shoulder may demonstrate narrowing of the subacromial space. Anatomic variations in the shape of the acromion, such as a hook or curve, are present in some people.  These variations, which are often visible on x-rays, can narrow the subacromial space and lead to impingement syndrome.

Treatment

Impingement syndrome is most often treated without surgery.  Non-surgical treatments include relative rest and avoidance of motions that provoke pain, ice, non-steroidal anti-inflammatory medications and physical therapy.   Steroid medication can be injected into the subacromial space if pain is not relieved by these other measures (see subacromial steroid injection).

In some cases, surgery is required to remove bone in order to create more space for the rotator cuff.