Spontaneous osteonecrosis of the knee (SONK)

Case contributed by Dr Ahmed Abdrabou


Severe right knee pain and swelling. No history of trauma

Patient Data

Age: 70 years old
Gender: Male

Extensive bone marrow edema of the medial femoral condyle exhibiting bright STIR signal and associated with linear subchondral fracture of the weight bearing surface of the femur displaying low signal in all pulse sequences as well as subtle flattening of the medial femoral condyle and joint effusion.

Diagnosis: Spontaneous osteonecrosis of knee stage II (MRI features)

Case Discussion

Differential diagnosis includes 

  • osteochondritis dessicans
  • osteoarthritis and 
  • stress fracture

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Case information

rID: 22634
Published: 12th Apr 2013
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

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