A and B, Anteroposterior radiograph and CT scan of a 16-year-old girl with a chondroblastoma of the femoral head. The lesion is epiphyseal and has a narrow zone of transition with a thin rim of reactive bone and a small amount of matrix mineralization. C, MR image demonstrates the lesion with extensive surrounding edema and an effusion. D, Extended curettage was performed through an anterior approach followed by the placement of a bone graft substitute  (E).