title: The Clinical Significance of Dark Cartilage Lesions Identified on MRI.
abstract: OBJECTIVE
  The purpose of this study was to determine the clinical significance of foci of low signal intensity in morphologically normal cartilage.
  
  
  METHODS
  This retrospective study included 887 patients who underwent 898 knee MRI examinations performed within 6 months of arthroscopic knee surgery. A musculoskeletal radiologist reviewed all MRI examinations for the presence of foci of low signal in cartilage where there was no visible morphologic abnormality, referred to as "dark cartilage lesions." The surgical reports of all patients were reviewed for the presence of cartilage degeneration at arthroscopy. Logistic regression was used to model the probability of dark cartilage lesions corresponding to cartilage degeneration at arthroscopy as a function of patient age.
  
  
  RESULTS
  In the 5388 articular surfaces assessed on MRI, 142 dark cartilage lesions were identified. The proportion of dark cartilage lesions corresponding to cartilage degeneration at arthroscopy was 52.0% (13 of 25) in the patella, 57.1% (28 of 49) in the trochlea, 90.9% (10 of 11) in the medial femoral condyle, 50.0% (two of four) in the lateral femoral condyle, 80.0% (four of five) in the medial tibial plateau, and 70.8% (34 of 48) in the lateral tibial plateau. There was a direct correlation (R(2) = 0.89) between patient age and the likelihood that a dark cartilage lesion would correspond to cartilage degeneration at arthroscopy.
  
  
  CONCLUSIONS
  Dark cartilage lesions may be found on every articular surface of the knee joint and may be a sign of otherwise occult cartilage degeneration.
authors.affiliation: 1 Department of Radiology, University of Wisconsin Clinical Science Center, E3/311, 600 Highland Ave, Madison, WI 53792.
authors.forename: B Keegan
authors.initials: BK
authors.lastname: Markhardt
authors.affiliation: 1 Department of Radiology, University of Wisconsin Clinical Science Center, E3/311, 600 Highland Ave, Madison, WI 53792.
authors.forename: Richard
authors.initials: R
authors.lastname: Kijowski
mesh_terms: D000328:Adult; D001182:Arthroscopy; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000473:pathology* / Q000601:surgery; D007719:Knee Joint / Q000473:pathology* / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008592:Menisci, Tibial / Q000473:pathology*; D008875:Middle Aged; D012189:Retrospective Studies
keywords: MRI; anisotropy; black line sign; cartilage