To examine the association between foot structure upon entry to military service and subsequent ankle injury during one year of follow-up.Background
Ankle injuries are common among athletes and military personnel; however, little is known about how measures of foot structure are associated with ankle injury risk in young and physically active populations.Methods and Measures
All incoming cadets at the United States Military Academy at West Point in the summer of 2013 were recruited to participate in this study. Study volunteers completed foot structural assessments within 3 days of arrival. Arch height and foot length were measured in sitting and standing positions, using a custom-made jig to calculate Arch Height Index to assess foot structure (planus, neutral, cavus). The primary outcome of interest was time from baseline until incident ankle injury during one year of follow-up. Univariate and multivariable Cox Proportional Hazards regression models were used to analyse the data. Kaplan-Meier survival estimates, hazard ratios (HR) and 95% confidence intervals (CIs) were calculated by foot structure.Results
Complete data for foot structure were available on 1090 subjects or 2180 feet (18.5±1.1 years, 1.76±0.80 m, 76.1±12.6 kg, and 24.5±2.96 kg/m2), of which 174 (16%) were female. In univariate models, subjects with neutral foot structure were at the greatest risk for incident ankle injury followed by planus foot structure during the follow-up period. Individuals with cavus foot structure were 52% less likely (HR=0.48; 95% CI=0.21, 1.12) to sustain an ankle injury during follow-up when compared to those with neutral foot structure. Results were similar in multivariable models controlling for sex and BMI for both sitting and standing measures of foot structure.Conclusions
These data suggest that cavus foot structure may be associated with reduced risk of ankle injury in young and active military populations.