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Shoulder Impingement Syndrome

What is Impingement Syndrome?

Shoulder impingement Syndrome refers to a type of shoulder pain that arises from injury to the tissues surrounding the shoulder joint.. It may be due to inflammation of either the shoulder tendons (tendinitis), or the fluid sac (bursitis). The shoulder has a group of muscles deep inside that help hold this ball and socket joint together. They are called the rotator cuff muscles. One of the rotator cuff muscles, the supraspinatus, travels through a bony arch or tunnel, over the ball and socket joint, on its way from the shoulder blade (scapula) to the upper arm bone (humerus). When the supraspinatus tendon becomes inflamed, it swells and is impinged in the bony tunnel (which is now too small for the swollen tendon). Hence the name impingement syndrome. In addition, there is a fluid sac, called a bursa, in this tunnel which can become inflamed and produce the impingement pain. Even though the tendon and bursa can both be involved, the symptoms produced are not easy to distinguish from each other; this is why the injury is called a syndrome and not just shoulder tendinitis or bursitis.

What Causes Impingement?

Shoulder impingement syndrome can occur as the result of a sudden, acute injury, or can be the consequence of overuse. The overuse type is by far the most common. With overuse, the supraspinatus tendon may be strained from excessive loading. An example of this occurs in baseball pitchers, where the tendon is used in deceleration. This loading phase of throwing, combined with pinching of the tendon produced by having the hand in an overhead position, produces swelling and results in the impingement syndrome. It can also be caused by muscle imbalance which allows abnormal movement that results in pressure being placed on the bursa and supraspinatus tendon.

A very delicate balance exists between different muscle groups around the shoulder. If the strong internal rotators of the shoulder (like the pectoralis and latissimus muscles) become over-developed relative to the smaller and weaker external rotator muscles (the infraspinatus and teres minor of the rotator cuff), the humeral head will migrate upward and impinge the tendon of the supraspinatus. This muscle imbalance is very common, since most activities strengthen the internal rotators and, unless specific exercises are done for the external rotators, a muscle imbalance will develop. Once this occurs, it may only be a matter of time before the symptoms of impingement syndrome begin to develop.

Impingement syndrome may also develop more easily in people with loose shoulder joints (multi-directional laxity or instability).

How Is Impingement Syndrome Diagnosed?

Impingement syndrome produces a certain set of symptoms and signs. People usually report pain that is made worse by activity. It may spread from the shoulder into the upper arm. It is also made worse by any overhead motions, and tends to wake people at night if they sleep either on the sore shoulder, or with their hands over their head. As it worsens, there is increasing pain at rest.

With lifting of the arm to the side (a motion called abduction), there is often a painful arc, where there is discomfort mid-way in the lifting motion, but no pain with the arm at the side, or when it is fully overhead. In addition, there are certain tests which can reproduce the impingement pain. Strength testing usually reveals weakness of the external rotators and abductors. X-rays of the shoulder are usually normal (because the muscle tendon and bursa do not show up on X-rays). However, there is occasionally a bone spur ,overgrowth on the acromion. In some cases there is calcium seen in the bursa (calcific bursitis) or in the tendon (calcific tendonitis).

How Is Impingement Syndrome Treated?

Each treatment plan is individualized with your physician and physical therapist, and progress should be monitored regularly. Treatment usually takes place in three phases:

Phase I: control pain and inflammation This consists of applying ice, resting and using modalities such as ultrasound. In addition, anti-inflammatory medication may be helpful in reducing tissue swelling and pain, particularly if there is an acute flare-up. If there is pain at night, modification of the sleeping position is also important.

Phase II: restore strength and function Since muscle imbalance is frequently a cause of impingement syndrome, strengthening of the rotator cuff muscles is one of the most important parts of treatment. The motions which are weak and painful (external rotation and abduction) are the most crucial to strengthen.

Phase III: return to exercise and sport It is important that the re-introduction of the offending activity is gradual. Since the activity being done at the time of the injury may have been responsible for producing a muscle imbalance, it is important to keep participation at a low level until the weaker muscles have had a chance to 'catch up' in strength.

With sports that have al lot of overhead activity, such as throwing (baseball), spiking (volleyball) or swimming, it is important to have a coach or other qualified individual look at the style, technique or mechanics of the motion. This is a good time to make any modification in the technique that might speed return to play and prevent recurrence of injury.

Other interventions are sometimes required if these treatments are unsuccessful. An injection of cortisone (which is anti-inflammatory medication) into the bursa (the subacromial space) Is often helpful when pain prevents full participation in strengthening or rehabilitative exercises. If pain relief is achieved, it is important to realize that the strengthening exercises still need to continue. If all of these methods fail to cure the problem, surgery to enlarge the bony tunnel may be necessary.

Can Impingement Syndrome Be Prevented?

Recognizing that certain activities produce muscle imbalance may help prevent impingement syndrome. It is advised that external rotation strengthening be incorporated into any exercise program which naturally strengthens the internal rotators. This helps prevent the imbalance leading to impingement. U~ of proper technique in overhead sports is also important in prevention.

Are There Any Special Considerations?

There are other conditions which mimic impingement syndrome due to some overlap in the clinical signs and symptoms. For example, tears of the rotator cuff can occur, and require different treatment, particularly if they are large. In addition, pain that at first appears ' to be impingement syndrome could arise from the neck. A reassessment by a physical therapist or physician is advised if the pain and function are not improving.

Medical Content reviewed and approved by Canadian Academy of Sports Medicine
©1994 Dr. W. H. Meeuwisse & Dr. G. O. Matheson
Sponsored by CIBA.

Edited for use for the joint Preservation Unit of BC by Cheryl Davies, RN, 2010.