Hip and knee replacement as a proxy measure for lower limb osteoarthritis in Scottish military veterans

Introduction Physical activity is an important component of military training. Although injuries and musculoskeletal disorders are the most common cause of medical retirement from the Armed Forces, the long-term risk of lower limb osteoarthritis in veterans is unknown. We used data on hip and knee replacement in Scottish military veterans as a proxy measure. Methods Retrospective cohort study of 78 000 veterans born between 1945 and 1995 and a comparison group of 253 000 non-veterans, matched for age, sex and area of residence, followed up for up to 37 years, using survival analysis to examine the risk of hip and knee replacement. Results Veterans were significantly less likely to undergo hip replacement than non-veterans, Cox proportional HR 0.87, 95% CI 0.80 to 0.95, p<0.001. There was no significant difference between veterans and non-veterans in respect of knee replacement, HR 1.02, 95% CI 0.94 to 1.11, p=0.643, and there was no difference in the ages at which veterans and non-veterans underwent joint replacement. People who had served for longest in the military had similar risk to those with the shortest service. Conclusions Based on the likelihood of undergoing joint replacement surgery in later life, we found no evidence of a positive association between military service and an increased risk of lower limb osteoarthritis.