Exploring flatfeet morphology in children aged 6–12 years: relationships with body mass and body height through footprints and three-dimensional measurements

The aim of the study was to determine the relationship between flatfoot morphology and body mass and height in children aged 6–12 years. A total of 6471 Chinese children (mean age 9.0 ± 1.9 years, 41% female) were assessed for foot morphometry, body height, and body mass index. Foot morphology, including foot length, width, girth, arch height, hallux valgus angle, and rearfoot valgus angle, was measured using a 3D laser scanner. Flatfoot evaluations were conducted using the Sztriter–Godunov index (KY) from footprints. All measurements were analyzed by age and sex using the mean values of the left and right sides. Comparisons were performed between flatfoot groups, between body mass index (BMI) groups, and between body height groups. The study revealed a significant decrease in the incidence of bipedal flatfoot with age ( p < 0.001), whereas the prevalence of obesity remained consistent ( p > 0.05). Bipedal flatfoot was associated with distinct morphological changes, including lower arches, reduced instep height, diminished ankle heights and a greater rearfoot valgus angle ( p < 0.05). When comparing the BMI groups, overweight children had larger and thicker feet ( p < 0.05), but no differences were found in arch height and ankle height ( p > 0.05). When comparing the body height groups, short-statured children had a shorter feet girth, shorter arches, and shorter ankle height ( p < 0.05), but no differences were found in the rearfoot valgus angle ( p > 0.05). Conclusion : The main characteristics of flat feet include lower arches and instep heights and ankle heights but higher rearfoot valgus angles. In general, overweight children’s feet do not have the common features of flat feet. In contrast, short children had similar features of flatfoot except for rearfoot valgus. Assessment of posture, such as rearfoot valgus, can be critical in identifying children with flat feet. What is Known: • The morphology of children's feet is associated with body growth, but the relationship between flatfeet and body mass and height remains controversial. What is New: • Three-dimensional foot measurement shows that body mass is generally not associated with flatfeet, while short children have lower arches but no rearfoot valgus.