Risk factors for patellofemoral pain in the military: Systematic review with meta-analysis

Abstract: BACKGROUND: The main cause for military training attrition is musculoskeletal injuries to the knee, such as patellofemoral pain (PFP). OBJECTIVE: To identify which factors increase the risk of PFP occurrence in military personnel. DESIGN: Systematic review with meta-analysis. DATA SOURCES: Searches were performed in MEDLINE/PubMed, CINAHL, Embase, SPORTDiscus, Web of Science, Scopus, and OpenGray databases. STUDY SELECTION: Included studies included military personnel and had a prospective cohort design investigating at least 1 variable as a risk factor for PFP. DATA EXTRACTION: Extraction was performed by 2 independent evaluators, and the data were separated between the military personnel who developed PFP and those who did not. DATA SYNTHESIS: Meta-analyses were performed using standardized mean differences (SMDs) and 95% CIs, and levels of recommendation were determined. RESULTS: From 11 articles, this review grouped 7518 military personnel, of whom 572 (7.61%) developed PFP. We found moderate evidence that isokinetic knee-extensor weakness at 60°/s predicts PFP in the military (SMD = -0.69; 95% CI = -1.02, -0.35). A larger frontal-plane knee-projection angle during the single-legged squat was also identified as a risk factor for PFP in male military personnel (SMD = 0.55; 95% CI = 0.14, 0.97) with a moderate level of evidence. We found moderate evidence that sex, body mass index, isometric knee-extensor strength, and isokinetic knee-flexor strength do not predict PFP in military personnel. Finally, we found strong evidence that age and body mass do not predict PFP in this population. CONCLUSIONS: Deficits in isokinetic knee-extensor strength and a greater frontal-plane knee-projection angle are risk factors for PFP in military personnel. Given that these are modifiable factors, these aspects should be considered in injury-prevention interventions in the military.