Editor’s note: This article is part of the Health and Fitness page’s weekly series about sports injuries based on information from the physical therapists of Cyclone Sports Medicine. This week, Mike Shaffer will spotlight shoulder instability.

A scorching fastball, a well-executed backstroke and an ironclad full nelson can be things of beauty, but these moves can come at a cost for athletes because the success of each one depends heavily on the shoulder joint.

Mike Shaffer, physical therapist at Cyclone Sports Medicine, said shoulder instability is a looseness of the shoulders that can be traumatic — caused by a single injury — or atraumatic — caused by repetitive motion.

Shaffer said shoulder instability usually occurs in people under the age of 40, and the earlier the injury occurs, the more likely it is that patients will be subjected to life-long shoulder problems.

“If someone under the age of 20 would suffer either a dislocation [a complete separation of the joint surface] or a subluxation [a partial disassociation of the joint surfaces], that individual has a nine out of 10 chance of having a recurrence of the episode,” he said. “The initial occurrence of instability or the possible recurrence of instability significantly declines with age, particularly over the ages of 30 or 40.”

As people age, they tend to be more selective about their range of movements, he said. For that reason, shoulder instability is more likely in younger athletes.

“As we age, our connective tissue gradually stiffens, and we also become more selective with regard to the activities we choose to participate in,” he said.

Atraumatic shoulder instability typically affects “overhead” athletes, such as volleyball players, swimmers, baseball players and softball players. The onset of shoulder instability also can be traumatic in wrestlers, rock climbers and skiers.

Shaffer said the shoulder is the most mobile joint in the body, and the ability to move freely comes at the expense of stability. This mobility is a function of the joint’s shape, as is its likelihood of injury.

“The ball and the socket are both convex,” he said. “It is like to trying to balance a basketball on a table.”

Several structures in the shoulder attempt to increase the stability of the shoulder, Shaffer said.

“There is a rim of cartilage that surrounds and deepens the socket. It is called the labrum,” he said. “There are several ligaments around the shoulder that serve to restrict motion. Most importantly, there is the rotator cuff. The rotator cuff is a group of four muscles that come together into a common tendon. These muscles help stabilize the ball and keep it aligned with the socket.”

The treatment for a traumatic dislocation or subluxation is a period of immobility followed by physical therapy. Shaffer said the next stage of rehabilitation is weightlifting to strengthen the rotator cuff.

“This can be accomplished either using free weights or an elastic band called a theraband. Patients would have to perform either internal rotation [pulling the palm in toward the stomach] or external rotation [pulling the palm away from the stomach] to strengthen the rotator cuff,” he said. “Strengthening of the shoulder blade muscles is also very important.”

As with many types of injuries, action can be taken in advance to limit the risks associated with traumatic or atraumatic shoulder instability, Shaffer said.

“Maintain a strong rotator cuff by regularly performing internal and external rotation strengthening exercises,” he said. “Secondly, choose your activities wisely.”

For further information, students, faculty and staff may visit Cyclone Sports Medicine, located in the Lied Recreation Center, or call 294-2626.