Background: The Foot Posture Index (FPI) is a clinical tool for diagnosis that aims to quantify the grade of a foot position as neutral, pronated, or supinated. Its purpose is to develop a simple six-factor method for rating foot posture with an easy and quantitative result. We evaluated possible differences in the FPI by sex and the influences of age, weight, height, foot size, and body mass index (BMI) on foot posture.
Methods: In 150 asymptomatic children (79 boys and 71 girls) aged 8 to 13 years, we determined weight, height, BMI, and FPI in the bipedal, static, and relaxed position. The FPI was obtained as the sum of the scores (-2, -1, 0, 1, 2) given to each of the six criteria.
Results: The mean ± SD FPI value for the total sample was 5.1 ± 2.1 (boys: 5.1 ± 2.2; girls: 5.2 ± 2.0), so there were no significant differences between the sexes (P = .636). Of the 150 feet examined, none had FPI values of very supinated or highly pronated, two were supinated (1.3%), 76 neutral (50.7%), and 72 pronated (48.0%). Of the total FPI values, 7.7% can be explained by anthropometric variables: height, weight, and foot size (r2 = 0.077; P < .010).
Conclusions: The most frequent foot postures in the sample were neutral and pronated. Neither age nor BMI explained variations in the FPI.