The illustrations show the US Risser grading system. (A) The US system comprises six grades. The US Risser 0 is defined as no ossification. The iliac wing is then divided into quarters, defining the first four grades (1, 2, 3, 4) of ossification of the apophysis (capping). The US Risser 5 begins when the ossified apophysis starts fusing to the wing at its posterior extremity. It continues during the whole process of apophysis fusion, which might take as much as 2 years. (B) The French Risser grading system also comprises six stages. French Risser 0 is defined as no ossification. The iliac wing then is divided into thirds, defining the first three grades (1, 2,3) of ossification of the apophysis (capping). The fusion of the apophysis to the wing is divided into two grades: Risser 4, when the fusion commences posteriorly, and Risser 5, when the fusion is complete. (Reprinted with permission from Bitan FD, Veliskakis KP, Campbell BC. Differences in the Risser grading systems in the United States and France. Clin Orthop Relat Res. 2005;436:190–195.)