MRI features are suggestive of spontaneous osteonecrosis of the knee (SONK) involving the medial femoral condyle. It is usually a diagnosis in an older age group (>55 years) with a female predilection and usually unilateral, mostly affecting medial tibial plateau. This type of knee disease occurs with no history of trauma, however being considered as an insufficiency fracture on top of osteoporosis. It is often associated with a meniscal tear.
MRI suggestive features are:
location: in the weight-bearing area, usually the medial femoral condyle
subtle flattening / focal depressive deformity
an irregular, discontinuous hypointense line in the subarticular marrow