Characterization of Patellofemoral Pain in the U.S. Military, 2016-2022.

INTRODUCTION: Patellofemoral pain (PFP) is a common musculoskeletal condition and a leading cause of medical encounters in the U.S. Armed Forces. Despite its impact on readiness, little is known about its incidence and clinical correlates in active-duty service members (ADSMs). MATERIALS AND METHODS: We conducted a retrospective analysis of ADSMs from 2016 to 2022 using the Medical Assessment and Readiness System. PFP was identified using ICD-10 codes. Demographics, comorbidities, and service branch were extracted from administrative and clinical records. Chi-square tests and Poisson regression estimated unadjusted associations, while multivariable generalized linear models (GLMs) assessed adjusted risk ratios (aRRs) for PFP and its sequelae, including subsequent knee osteoarthritis. RESULTS: Among 2,477,394 ADSMs, 85,023 (3.4%) had an initial PFP diagnosis, yielding an incidence rate of 0.94 per 100 person-years. The Army accounted for 47.0% of cases despite comprising 36.4% of the force. Female sex (aRR = 1.26, 95% confidence interval [CI]: 1.24-1.28), age 31-40 years (aRR = 1.32, 95% CI: 1.29-1.35), non-Hispanic Black race (aRR = 1.40, 95% CI: 1.38-1.43), vitamin D deficiency, hypertension, and hyperlipidemia were all independently associated with PFP. During follow-up, 4.4% of ADSMs with PFP developed knee osteoarthritis, compared with 0.9% without PFP, representing a 4-fold increased risk (aRR = 4.0; 95% CI: 3.9-4.1). CONCLUSIONS: PFP disproportionately affects Army personnel, and strongly predicts knee osteoarthritis. These findings highlight the need for targeted prevention and early management strategies to mitigate long-term disability and preserve military readiness.