The incidence of primary hip osteoarthritis in active duty US military servicemembers

Objective Although multiple studies have reported the prevalence of primary hip osteoarthritis (OA), little has been reported on incidence rates of hip OA. We sought to determine the incidence rate and demographic risk factors of hip OA in an ethnically diverse and physically active population of US military servicemembers. Methods A query was performed using the US Defense Medical Epidemiology Database for the International Classification of Diseases, Ninth Revision, Clinical Modification code for hip OA (715.95). Multivariate Poisson regression analysis was used to estimate the rate of hip OA per 100,000 person‐years, controlling for sex, race, age, rank, and service. Results The overall unadjusted incidence rate of hip OA was 35 per 100,000 person‐years. Women, compared with men, had a significantly increased adjusted incidence rate ratio for hip OA of 1.87 (95% confidence interval [95% CI] 1.73–2.01). The adjusted incidence rate ratio for black servicemembers when compared with white servicemembers was 1.32 (95% CI 1.23–1.41). The adjusted incidence rate ratio for the ≥40‐year‐old age group compared with the 20‐year‐old group was 22.21 (95% CI 17.54–28.14). With junior officers as the referent category, junior enlisted, senior enlisted, and senior officers rank groups had a significantly increased adjusted incidence rate ratio for hip OA. With the Air Force as the referent category, each service had a significantly increased adjusted incidence rate ratio for hip OA. Conclusion Female sex; black race; age ≥40 years; junior enlisted, senior enlisted, and senior officer rank groups; and military service in the Navy, Army, or Marines were all risk factors for hip OA.