Incidence of anterior cruciate ligament injury among active duty U.S. military servicemen and servicewomen

Although some studies have reported an increased incidence of anterior cruciate ligament (ACL) injuries in women athletes, little is known about the gender differences in injury patterns in the U.S. military. Using the Defense Medical Epidemiology Database, a search was performed for International Classification of Diseases, 9th Revision (ICD-9) codes 717.83 (old disruption of ACL) and 844.2 (sprain, strain cruciate ligament of the knee) among all servicemen and servicewomen between 1997 and 2003. Multivariate Poisson regression analysis was used to estimate the rate of ACL injuries per 1,000 person-years, controlling for age and race, for each ICD-9 code. We computed rate ratios and 95% confidence intervals (CIs) by using male as the reference category. The injury rates for code 717.83 were 3.09 cases per 1,000 person-years for men and 2.29 cases per 1,000 person-years for women, controlling for age and race (relative risk, 0.74; 95% CI, 0.71-0.76). The injury rates for ICD-9 code 844.2 were 3.79 cases per 1,000 person-years for men and 2.95 cases per 1,000 person-years for women, controlling for age and race (relative risk, 0.78; 95% CI, 0.76-0.80). There was not an observed increase in the incidence of ACL injuries among female soldiers in the U.S. military between 1997 and 2003.