The foot posture index: anthropometric determinants and influence of sex

The Foot Posture Index (FPI) quantifies foot posture on the basis of six criteria. Although the male foot is longer and broader than the female foot, limited evidence exists about the differences in foot posture between the sexes and which are its biological and anthropometric determinants. We sought to evaluate possible sex differences in the FPI and the determinants influencing foot posture.

In 400 individuals (201 men and 199 women), the FPI was determined in the static bipedal stance and relaxed position. The FPI was obtained as the sum of the scores (-2, -1, 0, 1, or 2) given to each of six criteria. A multiple regression model was constructed of the overall FPI against age, weight, height, body mass index, and foot size.

The mean ± SD FPI was 2.0 ± 4.3 overall, 1.6 ± 4.5 for men, and 2.4 ± 4.1 for women, with the difference being nonsignificant (P = .142). The neutral posture was the most frequent (57.3%). A greater proportion of women had neutral and pronated feet, and a greater proportion of men had supinated and highly supinated feet, with the differences being nonsignificant (P = .143). Foot size, height, and body mass index together explained 10.1% of the overall FPI value (P < .001).

The most frequent posture was neutral with a certain degree of pronation, with no differences in FPI values between men and women. Participants with larger foot sizes had higher FPI values, whereas taller and heavier participants had lower FPI values.