We studied the torsion angle of the tibio-fibular unit in both lower legs of 1588 schoolchildren of both sexes (998 girls and 590 boys), aged between 3 and 18 years divided into four age groups. The torsion angle of the tibio-fibular unit progressively increases with age. Stable values were measured only in the 11-15 years age group. Statistically significant differences of the torsion angle between one lower limb and the other were detected in the girls of the 6-10 and 11-15 age groups, and in the boys of the 6-10 age groups.