Background: Glenohumeral instability is a common injury sustained by young athletes. Surprisingly, little is known regarding the incidence of glenohumeral instability in collegiate athletes or the relevant risk factors for injury. A better understanding of the populations most at risk may be used to develop preventive strategies.

Hypothesis: The incidence of glenohumeral instability in collegiate athletics is high, and it is affected by sex, sport, type of event, and mechanism of injury.

Study design: Descriptive epidemiologic study.

Methods: The National Collegiate Athletic Association injury database was queried for all glenohumeral instability events occurring between the years 1989 and 2004. An analysis of the injuries was performed by sport, activity (competition versus practice), sex, type of event (primary versus recurrent), mechanism of injury, and time loss from athletic performance. Incidence rates and incidence rate ratios were calculated.

Results: A total of 4080 glenohumeral instability events were documented for an incidence rate of 0.12 injuries per 1000 athlete exposures. The sport with the greatest injury rate was men's spring football, with 0.40 injuries per 1000 athlete exposures. Overall, athletes sustained more glenohumeral instability events during games than practices (incidence rate ratio [IRR], 3.50; 95% confidence interval [CI], 3.29-3.73). Male athletes sustained more injuries than did female athletes (IRR, 2.67; 95% CI, 2.43-2.93). Female athletes were more likely to sustain an instability event as the result of contact with an object (IRR, 2.43; 95% CI, 2.08-2.84), whereas male athletes were more likely to sustain an event from player contact (IRR, 2.74; 95% CI, 2.31-3.25). Time lost to sport (>10 days) occurred in 45% of glenohumeral instability events.

Conclusion: Glenohumeral instability is a relatively common injury sustained by collegiate athletes. More injuries occurred during competition and among male athletes.