Prevalence of flatfoot and analysis of plantar pressure distribution in adolescents based on body mass index: a regional study.

Background: The foot is an essential organ for human locomotion. Assessment of plantar pressure distribution could provide key clinical information on foot functions. However, the mechanism that links body mass index to injury is not clear. The aims of this study were (1) to analyze the feature of plantar pressure distribution in Chinese adolescents and (2) to estimate the prevalence of flatfoot.

Methods: 1,217 participants aged 17-23 years (756 males and 461 females) were enrolled in this study. Static and dynamic foot-related variables, including contact area and plantar pressure, were measured. Based on BMI, participants were stratified into three groups: the underweight group (BMI < 18.5 kg/m²), the norm weight group (18.5 ≤ BMI < 25 kg/m²), and the overweight group (BMI ≥ 25 kg/m²). Mann-Whitney U test was used to compare the three different BMI groups.

Results: Overall, BMI had an impact on the contact area and plantar pressure at the 2nd to 4th metatarsal, 5th metatarsal, midfoot, and lateral heel, with greater pressure in these areas in the dynamic state. In particular, when shifting from the static phase to the dynamic phase, the plantar pressure of the forefoot shifted laterally. Moreover, the contact area, and plantar pressure at 2nd to 4th metatarsal, 5th metatarsal, middle foot, and lateral heel pressures were positively correlated with BMI. Among the 1217 participants, 67 adolescents were diagnosed with flatfoot.

Conclusions: This study confirms that BMI does influence plantar pressures and that each BMI classification displays unique plantar pressure characteristics in Chinese adolescents.