Jan. 5, 2005
ACC Sports Sciences Main Page
Scott C. Montgomery, M.D.
David R. Diduch, M.D.
University of Virginia Sports Medicine
Shoulder impingement is a pinching of the rotator cuff tendons between the bones of the shoulder. This can cause a spectrum of injuries from inflammation (bursitis and tendonitis) to a hole in the tendon (rotator cuff tear). There are two main types of shoulder impingement-external and internal. External or outlet impingement is typically associated with a compression of the cuff tendons against the underneath side of the acromion or roof. Internal impingement occurs in younger athletes who participate in overhead sports such as swimming, baseball, or tennis. The rotation of the shoulder and the distraction with the follow through causes micro-trauma to the posterior part of the shoulder capsule. This posterior capsule becomes scarred, tight, and painful and causes the humeral head to ride up in a higher position than usual in the cocking phase of throwing or when abducted and rotated. This higher position causes a pinching of the rotator cuff tendons between the humeral head and the shoulder socket (glenoid). The posterior capsular tightness, if it progresses long enough, reduces the internal rotation of the shoulder, causing stiffness, pain and increasing the risk of developing injuries to the under surface of the rotator cuff or superior shoulder labrum (SLAP lesions) by a "peel back" mechanism.
Who gets internal impingement?
The shoulder is a common source of injury in both elite level and recreational swimmers. External or outlet impingement occurs most commonly in masters level swimmers (over 40 years old) and can be associated with a full thickness rotator cuff tear. Internal impingement develops in young, active athletes involved in repetitive overhead activities. The most common athletes who get impingement are throwers (baseball pitchers, football quarterbacks) and swimmers.
History and physical examination are the keys to diagnosing internal impingement. Athletes complain of shoulder pain and may or may not complain of stiffness.
Range of motion and rotator cuff strength are important physical exam findings. Swimmers and throwers tend to have increased shoulder external rotation and decreased internal rotation as a result of training demands. This lack of internal rotation can cause shoulder problems and is called GIRD (Glenohumeral Internal Rotation Defecit). Internal rotation deficits are best checked while lying supine flat on a table (which stabilizes the scapula), bending the shoulder at a right angle (abducted 90-degrees) and then internally rotating the arms toward the feet. Both sides should be checked at the same time and compared. When a side-to-side difference of more than 20 degrees exists, then the diagnosis of GIRD in the affected shoulder is made, and the athlete is considered at risk to develop a SLAP lesion.
The rotator cuff tendons can be weak due to either inflammation or a partial thickness tear. This often coexists with a tight posterior capsule and relative anterior laxity in internal impingement.
Non-operative treatment (rehab)
The primary treatment for shoulder internal impingement is physical therapy. Rehabilitation efforts focus on stretching out the tight posterior capsule. This can be accomplished in therapy with a stretching program emphasizing internal rotation and forward flexion.
One stretch that is particularly effective and can be done at home is the sleeper stretch. This is done with the athlete lying on his affected side, shoulder at a right angle (abducted 90-degrees) and gentle but constant pressure pushing his arm down toward his feet in internal rotation with the other arm. It often helps for the athlete to lean in toward the affected arm for additional stretching. This stretch should be done a few times a day in addition to any formal therapy program.
Therapy programs are typically effective over several months, but patience is warranted as it may take longer. These programs work by stopping and possibly reversing any damage to the affected shoulder.
Further imaging of the shoulder is indicated if symptomatic improvement is not achieved with rehabilitation or there is concern for another cause of shoulder pain. Plain x-rays and magnetic resonance imaging (MRI) are often performed to rule out additional lesions and further examine the anatomy. Plain x-rays are usually normal. MRI with contrast dye often will show some posterior capsular scarring and thickness. Along with this, tendonitis or a partial tear of the rotator cuff tendons is quite common. Additional injuries to the shoulder labrum can also be seen.
Most athletes return to full performance with non-operative rehabilitation. If an organized therapy program is unsuccessful in eliminating the symptomatic internal impingement or posterior capsular tightness over a prolonged time period (usually 3-6 months), then surgery is indicated. Surgical treatment is arthroscopic and typically debrides (smoothes down) the underneath side of any partial rotator cuff tears. Any labral detachment or SLAP lesion can be repaired by suture reattachment, typically using suture anchors. Posterior capsular tightness can be arthroscopically released, and in unusual cases, any excessive anterior laxity can be tightened. It is important to note that the main "engine" driving the problem is the tight posterior capsule. The scope also allows a thorough evaluation of the shoulder joint to see if any thing else is injured. Surgical treatment is typically effective and is followed by additional rehab to gain and maintain the improved range of motion.
Return to the pool
Swimmers are ready to return to the pool when their range of motion and pain level allows. Although internal impingement can lead to shoulder pain and further injuries, recognition and a structured treatment program can get most swimmers back to competition.