June 2011 Newsletter

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Swimmer’s Shoulder
By Dr. Stephen A. Hunt

Swimming is a popular year-round competitive sport. It is estimated that 42,000 male and female swimmers have competed at the NCAA Division I level over the past 25 years. Recently, some studies have looked at the occurrence of injuries to swimmers in an attempt to identify who may be at risk for these injuries. While any body part can be injured during training and competition, the shoulder has the highest incidence of injury, with some reviews suggesting over 50% of all injuries in collegiate swimmers that result in lost practice or competitions are to the shoulder. "Swimmer's shoulder" is commonly thought of as an impingement of the shoulder with chronic irritation to the supraspinatus muscle (the top rotator cuff muscle).

The mechanics of the shoulder are extremely complex. It is comprised of muscles, bones, and ligaments. The muscles of the upper back and neck (latissimus and trapezius), the chest (pectoralis), as well as the shoulder muscles proper (the deltoid and rotator cuff) act in a fine balance to provide stability to the shoulder joint while providing power to the arm to propel the athlete through the water. If there is imbalance of strength or endurance, the shoulder blade (scapula) or the ball of the shoulder joint (humeral head) may move improperly and can cause the soft tissues of the rotator cuff to become pinched between the bones of the shoulder, resulting in a painful impingement syndrome commonly called "swimmer's shoulder" in this population.

The bony anatomy of competitive swimmers can contribute to some abnormalities in the joint motion and the creation of swimmer's shoulder, but more commonly the ligaments are a source of this problem. The ligaments of the shoulder are thickenings of the joint capsule ­add comma a type of connective tissue between the ball and the socket of the joint. In different positions of the overhead motion, specific ligaments provide stability to the ball within the socket. These ligaments are like ropes, they have a finite length and once taut, they cannot be stretched any further without tearing. Everybody has different tension of there ligaments. This is called laxity. Some people are born with very tight ligaments, and some are born with loose ligaments termed hyperlaxity. If you can hyperextend your knees or elbows, or touch your thumb to your forearm, then you probably have hyperlaxity. Because the strokes of swimming require such a high degree of shoulder motion, many elite swimmers have greater laxity than the average population.

The shoulder ligaments sit underneath the rotator cuff, which also provide stability to the ball and socket by providing dynamic tension (think of a bungee cord that has stretch but also gets tighter the further it is stretched). The looser the ligaments are, the more work the rotator cuff muscles have to perform to keep the ball centered on the socket. If the rotator cuff muscles fatigue, then the ball can drift around in the socket and cause the muscle to get pinched between the bones. This results in irritation of the rotator cuff tendon and the bursa (a fluid filled sack that overlays the tendon). Most swimmers will complain of pain with overhead motion or when they lift the arm out to the side away from their body. Some athletes may even feel the ball subluxate or shift out of the socket then quickly slide back into position, with a subtle or not so subtle click.

Other ways that this impingement can occur is when the shoulder blade doesn't move properly (scapular dyskinesis). This abnormal motion can be from a muscle problem around the scapula, or secondary to an impingement syndrome described above.

Risk factors for developing these problems include hyperlaxity, volume of training, and change in cross training regimen. The main treatments include modifying activities (volume of training), anti-inflammatory medications, and restoration of normal shoulder mechanics, both of the shoulder blade and the ball and socket joint (usually with a therapist). Occasionally an injection with steroid may decrease some of the sensitivity of the shoulder. MRIs may be helpful in cases that do not respond to several months of these treatments or other findings suggest a different diagnosis. Fortunately, surgery is rarely indicated for this problem.

REFERENCES:

1. Wolf BR et al. Injury patterns in division I collegiate swimming. Am J Sports Med 2009; 37 (10): 2037-2042.
2. McMaster WC et al. A correlation between shoulder laxity and interfering pain in competitive swimmers. Am J Sports Med 1998; 26 (1): 83-6.
3. Sein ML et al. Shoulder pain in elite swimmers: primarily due to swim-volume induced supraspinatus tendinopathy. Br J Sports Med 2010; 44:105-113.
4. Bak K and Fauno P. Clinical findings in competitive swimmers with shoulder pain. Am J Sports Med 1997; 25 (2): 254-60.
5. Richardson AB et al. The shoulder in competitive swimming. Am J Sports Med 1980; 8 (3): 159-63.