Subchondral Insufficiency Fracture
Imaging Findings:
• Circle demarcating the region of edema within the medial femoral condyle.
• There is T1- and T2-hypointense linear signal within the medial femoral condyle along the subchondral bone which does not involve the cortex.
Case description:
• Subchondral Insufficiency Fracture (SIF)
- previously coined as Subchondral Osteonecrosis of the Knee (SONK) but term not favored because lesion is insufficiency rather than osteonecrosis.
• Most common of the medial femoral condyle.
• See a linear T2- and T1-hypointense subchondral fracture line with marked surrounding marrow edema. Articular cartilage usually intact.
Differential diagnosis:
• Osteonecrosis - Curvilinear subchondral line of sclerosis with central marrow signal.
• Osteochondral defect (Osteochondral fracture) - Fracture line beyond medullary cavity into cortex and articular cartilage.
Dr. Donald von Borstel @DrvonBorstel
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