Age, Sex, Body Mass Index, and Laterality in the Foot Posture of Adolescents: A Cross Sectional Study

To investigate the relationship between the right and left foot posture in terms of body mass index (BMI), sex, and age in adolescents aged 10 to 14. A total of 1400 adolescents were included. For assessment, the Foot Posture Index (FPI-6) was used. Each foot was assessed and ranked as supinated, normal, or pronated by the sum of the FPI-6 criteria. Each criterion was scored on a scale of –2 to +2, with negative for supinated and positive for pronated posture. A linear mixed model with repeated measures was used for statistical analysis. Sex, BMI, and right and left foot are associated with FPI-6. The total score attributed for male sex (β = 0.29, P = .04) and the left foot (β = 0.73, P < .001) was higher (male right foot: mean ± standard deviation [SD], 3.09 ± 2.84, male left foot: 3.76 ± 2.80; female right foot: mean ± SD, 2.28 ± 2.61, female left foot: 3.45 ± 2.66; laterality for left foot: mean ± SD, 3.55 ± 2.71, laterality for right foot: mean ± SD, 2.82 ± 2.7). On the other hand, the correlation coefficient for the BMI was negative (β = -0.08, P = < .001), which means that the higher the BMI the lower the score attributed to the FPI-6. The FPI-6 is positively related to the male sex and the left foot—that is, the predicted score is higher, so the feet tend to present with a tendency to pronation. Although BMI is associated with FPI-6, it was not possible to establish a relationship between high BMI and pronation of the feet.