title: Association between medial meniscus extrusion and spontaneous osteonecrosis of the knee.
abstract: OBJECTIVE
  Medial meniscus tear has been proposed as a potential etiology of spontaneous osteonecrosis of the knee (SONK). Disruption of collagen fibers within the meniscus causes meniscal extrusion, which results in alteration in load distribution in the knee. Our purpose was to determine whether the extent of medial meniscus extrusion correlates with the severity of SONK in the medial femoral condyle.
  
  
  METHODS
  Radiological stage of SONK and femorotibial angle (FTA) were determined on knee radiographs. Ellipsoid volume of SONK lesion and meniscal pathology (degeneration, tear and extrusion) were evaluated by magnetic resonance imaging.
  
  
  RESULTS
  All the 18 knees with SONK in the present study showed substantial extrusion (≥ 3 mm) and degeneration of the medial meniscus. The extent of meniscal extrusion and FTA were strongly associated with the stage and volume of the SONK lesion. Multiple linear regression analysis revealed that medial meniscus extrusion and FTA were useful predictors of the volume of the SONK lesion.
  
  
  CONCLUSIONS
  There was high association of medial meniscus extrusion and FTA with the radiological stage and volume of the SONK lesion. Increased loading in the medial femoral condyle with greater extrusion of medial meniscus and varus alignment may contribute to expansion and secondary osteoarthritic changes of a SONK lesion.
authors.affiliation: Department of Orthopaedic Surgery, Kobe City Medical Center General Hospital, Kobe, Japan.
authors.forename: Tadashi
authors.identifier: http://orcid.org/0000-0002-0846-9300
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Department of Orthopaedic Surgery, Kobe City Medical Center General Hospital, Kobe, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ota
authors.affiliation: Department of Orthopaedic Surgery, Kobe City Medical Center General Hospital, Kobe, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Fujita
authors.affiliation: Department of Orthopaedic Surgery, Kobe City Medical Center General Hospital, Kobe, Japan.
authors.forename: Eijiro
authors.initials: E
authors.lastname: Onishi
authors.affiliation: Department of Orthopaedic Surgery, Kobe City Medical Center General Hospital, Kobe, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Iwaki
authors.affiliation: Department of Orthopaedic Surgery, Kobe City Medical Center General Hospital, Kobe, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamoto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001175:Arthrography; D003430:Cross-Sectional Studies; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging; D008297:Male; D008592:Menisci, Tibial / Q000000981:diagnostic imaging; D008875:Middle Aged; D010020:Osteonecrosis / Q000000981:diagnostic imaging / Q000209:etiology*; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D000070600:Tibial Meniscus Injuries / Q000150:complications* / Q000000981:diagnostic imaging
keywords: femorotibial angle; meniscal extrusion; meniscus; spontaneous osteonecrosis of the knee