Table 1:

Steinberg Classification System for femoral head avascular necrosis.

Stage	Findings
	No symptoms
0	Normal radiograph
	MRI non-specific
	Mild pain in the affected hip. or pain with internal rotation
1	Normal radiograph
	MRI diagnostic
	Worsening or persistent pain
2	Increased sclerosis or cysts in the femoral head
3	Subchondral collapse (crescent sign)
	Flattening of the femoral head
4	Normal joint space
5	Narrowing of the joint space with/without femoral head involvement
6	Advanced degenerative changes