Treatment and prognosis is dependent on the extent of T2 subchondral signal and size of subchondral lesion (7,9,17). If detected early and the subchondral lesion is small (one algorithm proposes less than 3.5 cm2) (7), nonsurgical management is appropriate. Nonsurgical management includes non-weight bearing versus protected weight bearing with a medial off-loader knee brace, analgesics, nonsteroidal anti-inflammatory drugs as needed, and potentially bisphosphonates (6,17). Weight bearing status is dependent upon symptoms. If the lesion is larger (>50% of the femoral condyle or lesion size is greater than 5 cm), patients do not improve nonoperatively, or radiographically after 3 months, there is an increased risk of collapse and surgical referral is indicated (7,10,13).
If there is pain out of proportion to the examination over the medial femoral condyle without trauma and normal radiographs (except for osteoarthritic changes), one should have a low threshold to order an MRI to detect early onset of SONK.
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