Background: Little is known of the incidence of shoulder instability, despite some evidence that it may be a common injury in young, athletic individuals. The goal of this study was to determine the incidence of shoulder dislocation in United States military personnel, as well as to identify the demographic risk factors for injury.

Methods: We performed a query of the Defense Medical Epidemiology Database with the code from the International Classification of Diseases, Ninth Revision, for acute shoulder dislocation for the years 1998 through 2006. An overall injury incidence was calculated, in addition to multivariate analysis, to determine independent risk factors among the following demographic considerations: sex, race, branch of military service, rank, and age.

Results: The overall incidence rate was 1.69 dislocations per 1000 person-years. Significant demographic risk factors were male sex, white race, service in the Army, junior enlisted rank, and an age of less than thirty years (p< 0.0001).

Conclusions: The incidence of shoulder instability among U.S. military personnel (1.69 per 1000 person-years) is considerably higher than previous reports for the general U.S. population (0.08 per 1000 person-years). Male sex, white race, and an age of less than thirty years were significant independent risk factors for injury.

Clinical Relevance: Shoulder dislocation is endemic in the military population. While this may not be generalizable to the general U.S. population, this incidence rate may be reflective of young, athletic cohorts. An improved understanding of the demographic groups at risk can be used to develop future preventive strategies.