Table 1 Staging system for Osteonecrosis of the Knee (OK) in Sickle Cell Disease [17]
Stage | Radiological findings |
|---|---|
1 | Normal appearance, accompanied by pain |
2 | Cystic or osteosclerotic lesions, or both, with a normal contour of the distal part of the femur or the proximal part of the tibia, or both, and with no subchondral flattening of the articular surface. |
3 | Presence of crescent sign. Flattening of the condyle or collapse of the subchondral bone plate with formation of a calcified plate and a clear sclerotic halo. Slightly narrowed joint space. |
4 | Osteoarthritic changes, such as spur formation and osteosclerosis, with a shallow concave articular surface at the osteonecrotic region |