Current concepts on osteonecrosis of the femoral head

Table 3 Steinberg staging system

Stage	Features
0	Normal radiograph, bone scan and magnetic resonance imaging
I	Normal radiograph, abnormal bone scan and or magnetic resonance imaging
	IA Mild (involves < 15% of femoral head)
	IB Moderate (involves 15% to 30% of femoral head)
	IC Severe (involves > 30% of femoral head)
II	Cystic and sclerotic changes in the femoral head
	IIA Mild (involves < 15% of femoral head)
	IIB Moderate (involves 15% to 30% of femoral head)
	IIC Severe (involves > 30% of femoral head)
III	Subchondral collapse (crescent sign) without flattening of the femoral head
	IIIA Mild (involves < 15% of femoral head)
	IIIB Moderate (involves 15% to 30% of femoral head)
	IIIC Severe (involves > 30% of femoral head)
IV	Flattening of the femoral head/femoral head collapse
	IVA Mild (involves < 15% of femoral head)
	IVB Moderate (involves 15% to 30% of femoral head)
	IVC Severe (involves > 30% of femoral head)
V	Joint space narrowing and/or acetabular changes
	VA Mild
	VB Moderate
	VC Severe
VI	Advance degenerative joint disease