| I | involvement of anterior epiphysis without metaphyseal reaction, sequestrum or subchondral fracture line. < 25% epiphysis is involved |
| II | more extensive or severe involvement of anterior epiphysis, preservation of medial and lateral segments. Sequestrum present, with anterolateral metaphyseal reaction. Subchondral fracture line that doesn’t extend to the apex of femoral epiphysis. Less than half of epiphysis is involved. |
| III | entire epiphysis is dense, diffuse metaphyseal reaction with femoral neck widening. Subchondral fracture seen posteriorly. Most of epiphysis involved. |
| IV | total involvement of epiphysis, flattening, mushrooming and eventual collapse of femoral head. Extensive metaphyseal reaction and associated posterior remodeling |