We determined the skeletal age in 26 children (12 girls, 14 boys) with Osgood-Schlatter disease using knee radiographs. The average chronological age was 13.2 +/- 2.2 years, and the average bone age was 13.1 +/- 2.3 years (p > 0.01). All but one of the skeletal ages fell within the normal range. Skeletal maturation in children with Osgood-Schlatter disease is thus normal. With normal skeletal maturation and normal physes histologically (previously shown), it is unlikely that an abnormality of physeal development or structure is the etiology of Osgood-Schlatter disease. Rather, it is most likely a result of tensile stresses on the tibial tuberosity. This is in contrast to slipped capital femoral epiphysis, another common disorder affecting children of the same ages as those with Osgood-Schlatter disease, in which physeal abnormalities and skeletal maturation anomalies do occur.