Prevalence, incidence, and progression of hip osteoarthritis in a young military population: The ADVANCE cohort study

Objective: Prevalence of hip osteoarthritis (OA) is rarely reported in young populations (e.g., military). We will report the prevalence of hip OA in a young military cohort and investigate the relationship between injury and progression/incidence. Design: ADVANCE is a prospective cohort study comparing physical and psychosocial outcomes in 1145 men who served in Afghanistan including 579 men with combat injury (Exposed) who were frequency-matched to 566 controls (Unexposed). The Exposed group was sub-divided into hip injured (Exp-H), lower limb amputation (Exp-A) and other (Exp-NA). Kellgren-Lawrence (KL) scores of pelvic radiographs and Non-Arthritic Hip Score (NAHS) questionnaires were collected across two waves (Baseline and Follow-up). Prevalence at Baseline (KL ​≥ ​2), progression (KL ​≥ ​1 ​at Baseline, KL ​≥ ​2 ​at Follow-up) and incidence (KL0 at Baseline, KL ​≥ ​2 ​at Follow-up) at Follow-up were reported and compared between groups for KL and NAHS. Results: Baseline prevalence of radiographic hip OA was 8.5 ​% and 4.4 ​% in the Exposed and Unexposed groups, respectively. Exp-A and Exp-H groups had 3.88 (95%CI:2.27–6.63) and 7.18 (95%CI:3.44–14.98 times increased risk for radiographic hip OA than Unexposed. Exp-A and Exp-H had a 2.15 (95%CI:1.22–3.80) and 3.28 (95%CI:1.42–7.59) times increased radiographic progression risk, compared to Unexposed. Risk of NAHS Progression and Incidence were not significantly different between groups. Conclusion: Radiographic hip OA prevalence is higher in a young military population than in a similarly aged general population. Combat injury alone may not increase hip OA prevalence; but hip and lower limb loss injuries do. Progression risk is highest in those with hip or limb loss injuries.