Pre-academy knee pain as a predictor of overuse knee injuries in first-year military cadets.

Abstract

Introduction: Musculoskeletal injuries, particularly overuse knee injuries, pose a significant challenge to military readiness, accounting for over 50% of medical visits and substantial healthcare costs. Military academy training presents unique physical demands, with cadets undergoing 15-20 hours of physical training weekly. This study aimed to determine whether a history of knee pain, independently or combined with other injuries, influences the rate of overuse knee injuries among first-year military cadets.

Methods: 5820 first-year cadets from US service academies completed baseline questionnaires assessing 6-month pre-academy injury history. Overuse knee injuries during the first academic year were identified using Defense Medical Surveillance System data. Risk ratios (RR) and incidence rate ratios (IRR) were calculated to compare injury risk and rate between cadets with different injury histories, adjusting for sex, age, academy and year.

Results: The overall incidence rate was 240 overuse knee injuries per 1000 person-years. Incidence rates varied substantially by injury history-149 per 1000 among those without prior injury versus 613 per 1000 among those with prior knee pain only. Cadets with prior knee pain demonstrated significantly higher risk (RR=3.09; 95% CI 2.63 to 3.65; p<0.001) and rate (IRR=4.08; 95% CI 3.31 to 5.02; p<0.001) of overuse knee injury compared with those without prior lower extremity injury. Notably, the combination of prior knee pain with other injuries did not produce additive risk effects, suggesting anatomically specific injury history may be the primary driver of future injury risk.

Conclusion: Rather than implementing resource-intensive screening methods, careful assessment of prior knee pain history provides a practical approach for identifying high-risk cadets who could benefit from targeted screening and prevention strategies during their first year of military training.