In adults, a tibiofibular clear space (i.e., distance from the incisura fibularis to the medial fibula) of > or = 6 mm or a loss of tibiofibular overlap has been reported to correlate with injury to the distal tibiofibular syndesmosis. We reviewed anteroposterior (AP), lateral, and mortise ankle radiographs from 106 children (50 boys, 56 girls) aged 1-15 years in an attempt to assess whether these criteria are applicable to children. The incisura was detectable at a mean age of 8.2 years for girls and 11.2 years for boys. The range of tibiofibular clear space among the 48 children with a detectable incisura was 2-8 mm; seven (23%) of these 48 children had a clear space of > or = 6 mm in one or more views. The mean age at which the tibiofibular overlap began to appear on the AP view was 5 years for both genders, whereas on the mortise view, it was 10 years for girls and 16 years for boys. The criteria used to evaluate the integrity of the distal tibiofibular syndesmosis in adults do not apply to children in this normal study population.