The incidence of patellar dislocation injuries among US service members was an order of magnitude greater than that previously reported in civilian population studies. Gender, age, race, rank, and branch of military service are important risk factors related to the incidence of patellar dislocation injuries in this population.

Objective. To examine the incidence of osteoarthritis and the influence of demographic and occupational factors associated with this condition among active duty US service members between 1999 and 2008.Methods. To determine the total number of incident cases of osteoarthritis, the Defense Medical Surveillance System (DMSS) was queried by sex, race, age, branch of military service, and rank using code 715 of the International Classification of Diseases, Ninth Revision, Clinical Modification. Multivariable Poisson regression analysis was used to estimate incidence rates, rate ratios, and 95% confidence intervals (95% CIs) for osteoarthritis per 1,000 person-years.Results. A total of 108,266 incident cases of osteoarthritis were documented in the DMSS within a population that experienced 13,768,885 person-years at risk of disease during the study period. The overall unadjusted incidence rate among all active duty US service members during the study period was 7.86 cases per 1,000 person-years. Significant demographic and occupational risk factors for osteoarthritis included sex, age, race, branch of service, and rank (P < 0.001). Women experienced an adjusted incidence rate for osteoarthritis that was nearly 20% higher than that for men (rate ratio 1.19 [95% CI 1.17-1.21]). Service members ages >40 years experienced an adjusted incidence rate for osteoarthritis that was ϳ19 times higher than that for those ages <20 years (rate ratio 18.61 [95% CI 17.57-19.57]). Black service members experienced significantly higher incidence rates of osteoarthritis than those in the white and "other" race categories.Conclusion. Rates of osteoarthritis were significantly higher in military populations than in comparable age groups in the general population.Osteoarthritis is considered to be the most common form of arthritis, affecting an estimated 26.9 million adults ages Ն25 years in the US (1), and osteoarthritis accounts for Ͼ25% of all arthritis-related healthcare visits (2). The economic burden of direct and indirect costs associated with osteoarthritis is also significant, likely exceeding $60 billion annually (1,3-5). Although osteoarthritis has traditionally been considered a disease that affects older individuals, in whom the incidence increases with advancing age, recent studies suggest that the majority of adults with osteoarthritis are younger than age 65 years (6). Occupational physical demands (7,8) and traumatic joint injury (9,10) have been associated with the development of osteoarthritis. Studies also suggest that physical activity involving repetitive joint loading may be associated with the occurrence of osteoarthritis (11,12).Despite the burden associated with osteoarthritis, population-based estimates of the incidence of this condition are limited (6,13). Studies that have estimated incidence rates for osteoarthritis have typically focused on a single joint, and their findings may not represent the overall incidence of the disease (6,8,14). The majority of population-based studies have estimated the prevalence,...

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.