Risser sign for skeletal maturity

The iliac apophysis ossifies in a stepwise fashion from anterolateral to posteromedial along the iliac crest. The Risser sign is a visual grading of the degree to which the iliac apophysis has undergone ossification and fusion; it is used to assess skeletal maturity. Risser grade 0 corresponds to no ossification. As depicted above, grade 1 describes up to 25% ossification; grade 2 describes 26 to 50% ossification; grade 3 describes 51 to 75% ossification; grade 4 describes greater than 76% ossification; and grade 5 describes full bony fusion of the apophysis.