To estimate the relationship between obesity, general joint laxity and hypermobility of Chopart joint with flat foot in puberty, 3260 junior high school children's feet were analysed
1) Many cases with flat feet were revealed to have joint laxity or hypermability of Chopart joint, compared with normal foot.
2) Obesity itself was supposed to have no influence on the foot's arch, but when Chopart joint had hypermobility, obesity had a great influence on it.