title: Subchondral insufficiency fracture of the knee: A recognizable associated soft tissue edema pattern and a similar distribution among men and women.
abstract: OBJECTIVE
  Primary: to describe the presence and pattern of soft tissue edema in subchondral insufficiency fractures of the knee (SIFK). Secondary: to investigate the gender distribution and identify factors associated with disease progression.
  
  
  METHODS
  MR images of 74 SIFKs in 74 patients were retrospectively reviewed for soft tissue edema presence and location, meniscal tears and extrusion and synovitis. The clinical records were reviewed for age, gender, and BMI. Follow up examinations were reviewed to assess for progression. Data were analyzed for gender distribution and for association between each imaging finding as a predictor of SIFK location and progression.
  
  
  RESULTS
  Soft tissue edema was present in 89% (66/74) of SIFK. It was located around the MCL in 78% (58/74), posterior to and abutting on the posterior distal femur in 68% (50/74), around to the tibia in only 18% (13/74), but when present it strongly predicted the presence of a medial tibial plateau SIFK (p=5.6×10^-12). Edema extended to the vastus medialis fascia in 51% (38/74) and vastus lateralis fascia in 24% (18/74). Gender distribution was 1:1 (males=38, females=36), most common in the 6th decade (29/74, 39%). Lesion progression showed a trend towards being more common in females (8/9, 89%) compared to males (9/16, 56%), and in patients with meniscal extrusion (≥3mm) (13/14, 93%) compared to those with no extrusion (2/7, 29%).
  
  
  CONCLUSIONS
  A recognizable soft tissue edema pattern is seen in SIFK and may have an important role in early diagnosis. Also, SIFK may affect equally males and females in the 6th decade and may progress more in females. Meniscal extrusion may predispose to disease progression.
authors: Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, United States; Department of Radiology, UPMC Department of Radiology, 200 Lothrop Street, UPMC Montefiore, Room NE 595, Pittsburgh, PA 15213, United States. Electronic address: wilmotas@upmc.edu.
authors: Andrew S
authors: AS
authors: Wilmot
authors: Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, United States; Michael J. Crescenz VA Medical Center in Philadelphia, 3900 Woodland Avenue, Philadelphia, PA 19104, United States. Electronic address: aruutiainen@gmail.com.
authors: Alexander T
authors: AT
authors: Ruutiainen
authors: Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, United States; Princeton Radiology Associates, Kendall Park, NJ 08824, United States. Electronic address: ptbakhru@gmail.com.
authors: Prashant T
authors: PT
authors: Bakhru
authors: Stonybrook "University Medical Center, Stonybrook, NY, United States. Electronic address: Mark.Schweitzer@stonybrookmedicine.edu.
authors: Mark E
authors: ME
authors: Schweitzer
authors: Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, United States; Department of Radiology, HaEmek Medical Center, Afula, Israel. Electronic address: shabshin@gmail.com.
authors: Nogah
authors: N
authors: Shabshin
mesh_terms: D000328:Adult; D000368:Aged; D003238:Connective Tissue / Q000473:pathology*; D018450:Disease Progression; D004487:Edema / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D015775:Fractures, Stress / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000473:pathology; D006801:Humans; D015994:Incidence; D007718:Knee Injuries / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000473:pathology; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008592:Menisci, Tibial / Q000000981:diagnostic imaging* / Q000473:pathology; D008875:Middle Aged; D012189:Retrospective Studies; D012737:Sex Factors; D000070600:Tibial Meniscus Injuries / Q000000981:diagnostic imaging* / Q000473:pathology; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: Insufficiency fracture; Knee; Meniscus; Osteoarthritis; Spontaneous osteonecrosis of the knee