Table 4.

Ficat and Arlet classification [32] (modified) for osteonecrosis

Stage	Findings
0	Radiography: normal MRI: normal Clinical symptoms: none
1	Radiography: normal or minor osteopaenia MRI: bone marrow oedema Bone scan: increased tracer uptake Clinical symptoms: groin/hip pain
2	Radiography: mixed osteopaenia and/or sclerosis and/or subchondral cyst-like changes, without any subchondral lucency MRI: geographical signal change Bone scan: increased uptake Clinical symptoms: pain and stiffness
3	Radiography: crescent sign (subchondral lucency/fracture) and eventual cortical collapse MRI: femoral head collapse, joint preserved Clinical symptoms: pain and stiffness, limp
4	Radiography: end-stage with evidence of secondary OA MRI: femoral head collapse and OA Clinical symptoms: pain and limp

MRI – magnetic resonance imaging, OA – osteoarthritis