Overuse injuries can be caused by repetitive stress upon muscles, tendons, nerves and bones. This stress causes microscopic damage to these tissues. Often the body does not have enough time to repair the damage between bouts of exercise. About 750,000 overuse injuries will occur in young athletes each year. Many of these are avoidable.
The shoulder joint is highly mobile and allows us to reach overhead, out to the side, behind the back, and across our body to touch the opposite shoulder. This mobility also allows to us to throw overhand. The price we pay for such mobility is that we have less stability of the shoulder joint than other joints in the body. The stabilizing forces about the shoulder are quite complex. There are a set of ligaments that attach the head of the arm bone (humerus) to the socket of the shoulder (glenoid). These ligaments provide static stability to the shoulder joint. There are four muscles known as the rotator cuff, these supply much of the dynamic stability to the shoulder joint. There are other muscles that stabilize the wing bone (scapula) to the body. These are also important for shoulder stability.
In a physically immature athlete, the development of these muscles, tendons, and ligaments are not complete. They have not reached their maximal strength and are susceptible to being stretched, torn, and overwhelmed by repetitive stresses, such as throwing. This tearing, stretching, etc. often presents itself as pain to the young athlete.
Young athletes who are most likely to experience overuse injuries in the shoulder are pitchers, swimmers, and quarterbacks. Many times the overuse injuries can be rehabilitated through a program of rest, followed by exercises to strengthen these shoulder muscles.
Often the presenting signs or symptoms of a young athlete who is in the throws of overuse syndrome include a change in body mechanics during activity. ie. a change in mechanics while pitching a baseball. In fact, young throwing athletes, because of this change in mechanics, will place increased stress across the elbow and often complain of elbow pain before they complain of shoulder pain.
The velocity and accuracy of their throwing will be decreased as their overuse syndrome continues. They will eventually complain of shoulder pain.
Some of the syndromes in the shoulder related to repetitive throwing include “little leaguer shoulder”. This is actually a stress fracture of the growth plate located in the upper arm bone. This has been well documented with x-ray examination and requires absolute rest from throwing, if not, there is potential to disrupt and alter the growth plate of the upper arm.
Another syndrome called tendonitis can occur in one of the rotator cuff tendons or in the biceps tendon. It is a painful condition that is usually the result of poor mechanics or throwing too hard with a tired arm. The muscle-tendon unit can become inflamed secondary to microsopic tearing. A burning pain is often felt especially with release and follow-through of the ball.
When the rotator cuff tendons are over stressed and become tired. They can no longer protect the integrity of the joint. The ligamentous capsule of the joint is the next structure to be stressed. This capsule can be stretched which then may lead to permanent instability problems of the shoulder.
Shoulder injuries in the young athlete need to be recognized and treated promptly. The classic signs are pain, favoring the limb, change in throwing mechanics, or a change in accuracy and velocity. Treatment of these conditions should include rest and ice for several days followed by therapy to strengthen the appropriate muscles. Many of the organized little leagues now restrict the amount of throwing by a child, including innings pitched per game and/or per week.
To avoid overuse injuries, youngsters involved in throwing sports need to be monitored closely by their parents and coaches. At the first sign of a problem, treatment should ensue. This rest period should be approximately two weeks before return to limited throwing is undertaken. In a skeletally immature athlete, it is much better to be safe than sorry when dealing with overuse injuries.
Joseph J. Calandra, M. D.