Table 1.

Steinberg stages of osteonecrosis of the hip (30)

Stage	Criteria
0	Normal or nondiagnostic radiograph, bone scan, MRI
I	Normal radiographs; abnormal bone scan and/or MRI A–Mild (<15% of femoral head affected) B–Moderate (15%–30%) C–Severe (> 30%)
II	Cystic and sclerotic changes in femoral head A–Mild (<15% of femoral head affected) B–Moderate (15%–30%) C–Severe (>30%)
III	Subchondral collapse (crescent sign) without flattening A–Mild (<15% of articular surface) B–Moderate (15%–30%) C–Severe (>30%)
IV	Flattening of femoral head A–Mild (<15% of surface and < 2 mm depression) B–Moderate (15%–30% of surface and 2–4 mm depression) C–Severe (>30% of surface and > 4 mm depression)
V	Joint narrowing or acetabular changes A–Mild* B–Moderate* C–Severe*
VI	Advanced degenerative changes

^*Average femoral head and estimated acetabular involvement.