Sports Medicine Report: Shoulder Impingement
By Alicia McQuain, PT


Divers are very susceptible to shoulder problems. Such injuries can be recurrent and ultimately affect elite performance. Oftentimes shoulder pain can be contributed to an inflammatory response such as tendinitis or impingement. The first line of defense relies on early detection and is nonsurgical. Effective treatment for this condition requires a good understanding of anatomy, biomechanics and pathophysiology.

Anatomy
The shoulder is made up of two primary bones, the humerus (arm bone) and the glenoid (socket). Besides this primary joint, there are also many surrounding structures that affect arm movement. These include the collar bone, spine, sternum and shoulder blade. The shoulder or glenohumeral joint resembles a golf ball resting on a tee, with the humeral head as the ball and the glenoid as the tee. So, the shoulder has a wide range of movement without much bony stability.

There are numerous muscles that move and support the shoulder joint. One of the primary muscle groups is the rotator cuff that is comprised of four muscles including the supraspinatous, infraspinatous, teres minor and subscapularis. The supraspinatous tendon runs on top of the shoulder joint and under the roof formed by the end of the clavicle. It can easily be jammed between these two structures resulting in impingement and pain.

Biomechanics
The shoulder sacrifices stability for mobility. Its wide range of movement allows divers to enter the water cleanly. Any activity that involves forceful movement of the shoulder overhead, either by raising it in front (flexion) or to the side (abduction) combined with rotating the arm inward, causes an increase in irritation to the rotator cuff tendon (supraspinatous). Divers utilize this motion during takeoff, flight and entry. Rotator cuff muscles usually pull down on the humerus to keep it from jamming the supraspinatous tendon. However, if these muscles are weak, continual repetitious movement will result in impingement and pain.

Pathophysiology
Impingement can be defined as shoulder pain due to irritation to the supraspinatous tendon or bursa (sac of fluid). Both structures lay between the humerus and the acromion (roof of the shoulder joint). Primary impingement is due to crowding under the acromion caused by a genetically narrower space allowing easy pinching or jamming of the tendon and bursa. Secondary impingement is due to a decline in space created by decreased shoulder stability, resulting in weakness of rotator cuff muscles and scapular stabilizers. The resulting overuse and overstretching of the suprapinatous tendon causes shoulder pain.

Treatment
When an athlete develops signs of impingement, pain persists on the top and front of the shoulder especially with any overhead activity. A painful arc is usually present when the arm is between 90 and 120 degrees. In the beginning stages of impingement, inflammation is reversible. As the problem continues and becomes recurrent, the tendon may thicken and tear. Spurring may result and surgery could be necessary. A continuous cycle of factors lead to impingement and its progression.

Impingement can be stopped if a condition is treated early and the underlying cause corrected. The first line of defense is to decrease inflammation. Modalities such as ultrasound or electrical simulation and ice can work. Anti-inflammatory medications are also helpful initially. Aiding to correct postural faults, taping the shoulder into retraction (McConnel taping) may allow enough pain relief to progress with rehab. The tape pulls the humerus into retraction and an externally rotated position that decreases impingement until rotator cuff and scapular muscles are strengthened.
Once pain and inflammation are decreased, strengthening and stretching may progress. This program is a vital component in the prevention of future occurrences. Rotator cuff strengthening should be of primary importance as this improves the humeral head depression and keeps the tendons and bursa from being pinched.

Strengthening needs to be done in a variety of ranges using weights or resistive bands. Focus on technique and not compensating with the shoulder elevators or trunk should be emphasized. The scapula muscles need to be strengthened to pull the shoulder blades back and improve posture. This will help pull the humeral head back so it is not resting forward in the joint and pinching down on the tendon and bursa. Exercises such as rows, pull down and wall push ups are effective.

Stretching should also be an integral part of the program. The chest or pectoralis muscles in divers easily become overdeveloped and tight while contributing to poor posture. A door stretch is an easy way to stretch these muscles. Also, the posterior part of the shoulder capsule tends to become tight as the humerus rests forward. Pulling the arm across the front of the chest toward the opposite shoulder can stretch the back of the capsule.

Pain needs to be diminished and inflammation resolved prior to aggressive strengthening and full return to activity. The diver can begin with arm exercises in the water. In returning to their event, the athlete must progress slowly. Starting with less intense training, the athlete can monitor their capabilities and let pain be the deciding limitation.

If the athlete overtrains, the vicious impingement cycle can resume. If so, the athlete will have stepped back instead of returning to full capacity. Corrections in the dive position to avoid overstress to the shoulder may also be needed. Any time a diver experiences continual shoulder pain, evaluation by an athletic trainer, physical therapist or physician to determine the condition and treatment should be sought.

References
Andrews, J.R. and G.L. Harrleson. Shoulder Rehabilitation. Physical Rehabilitation of the Injured Athlete. Philadephia: W.B. Saunders Company, 1991, 367-442.
Greenfield G. and W. Stanish. Relieving Shoulder Pain Without Surgery. Physicians and Sports Medicine. 22:4:67-82: 1994.
Magee, D. Shoulder. Orthopedic Physical Assessment. (2nd Edition) Philadelphia: W.B. Saunders Company, 1992, 90-142.
Wilk, K., C. Arrigo, and J. Andrews. Current Concepts: The Stabilizing Structures of the Glenohumeral Joint. Journal of Orthopedic and Sports Physical Therapy. 25:6:364-379: 1997.

Alicia McQuain is a staff physical therapist with Spectrum Rehabilitation of the Christ Hospital in Cincinnati. As a graduate of the University of Kentucky, she has three years experience in the evaluation and treatment of orthopedic and sports injuries.