Spontaneous Osteonecrosis of Knee After Arthroscopy Is Not Necessarily Related to the Procedure

Reports in the literature have suggested a causal relationship between knee arthroscopy and spontaneous osteonecrosis of the knee (SONK). We conducted a study to determine if there are imaging characteristics associated with SONK and if there is a relationship between arthroscopy and SONK. In this retrospective review, we compared preoperative and postoperative findings in 11 patients (12 joints) who developed SONK after arthroscopy with findings in 11 age- and sex-matched controls who did not develop SONK after arthroscopy. There were no significant preoperative radiologic differences between the SONK and control groups. All 12 SONK lesions seen on magnetic resonance imaging were in the medial femoral condyle. Six SONK knees developed the lesion after arthroscopy, and 6 had SONK lesions before arthroscopy. Eleven of the 12 SONK knees had a medial meniscal tear, compared with 8 medial meniscal tears and 3 lateral meniscal tears in the control group. Eight SONK knees and 5 control patients had medial meniscal extrusion of more than 3 mm. A causal relationship between knee arthroscopy and SONK is questionable.