Table 2.

Steinberg staging system for hip osteonecrosis [60].

Stage	Imaging
0	Normal imaging
I	Normal radiographs. Abnormal bone scan and/or MRI
	A- Mild (<15% femoral head involvement)
	B- Moderate (15–30% femoral head involvement)
	C- Severe (>30% femoral head involvement)
II	Cystic and sclerotic changes
	A- Mild (<15% femoral head involvement)
	B- Moderate (15–30% femoral head involvement)
	C- Severe (>30% femoral head involvement)
III	Subchondral collapse without femoral head flattening
	A- Mild (<15% femoral head involvement)
	B- Moderate (15–30% femoral head involvement)
	C- Severe (>30% femoral head involvement)
IV	Femoral head flattening/collapse
	A- Mild (<15% femoral head involvement)
	B- Moderate (15–30% femoral head involvement)
	C- Severe (>30% femoral head involvement)
V	Joint space narrowing and/or acetabular changes
	A- Mild
	B- Moderate
	C- Severe
VI	Advanced disease