- Similar appearances to osteochondritis dissecans of the knee but is found in an older age group.
- SONK is not thought to be caused by bone death but may be caused by osteoporosis and insufficiency fractures.
- It is almost always unilateral, usually affects the medial femoral condyle
- Often associated with meniscal tear
- MRI is the best imaging modality: a focal subchondral area of low signal intensity adjacent to the subchondral bone plate and representing local ischaemia, this area does not enhance due to lack of blood flow.
- Late complication: secondary OA, secondary osteonecrosis
– Conservative treatment is favored – early treatment reduces risk of progression to subchondral collapse and osteonecrosis.: limitation of weight-bearing of the affected limb, NSAIDs for symptoms
– Surgery for refractory/progressed cases: total knee arthroplasty, osteochondral allografts