Table 1.

Differences between the original and simplified K&M classifications

Simplified K&M classification	Original K&M	Final radiographic description
Group 0 No ON	No ON	No signs of ON
Group A Nonsignificant ON	Group I	Changes affecting ossific nucleus but resulting in an essentially normal head at final followup
Group B Significant ON	Group II Group III Group IV	Lateral physeal damage resulting in coxa valga Central physeal damage resulting in coxa breva Total damage to head and physis resulting in deformity of femoral head and neck

K&M = Kalamchi and MacEwen classification; ON = osteonecrosis.