title: A practical MRI grading system for osteoarthritis of the knee: association with Kellgren-Lawrence radiographic scores.
abstract: OBJECTIVE
  To propose a reproducible and constant MR grading system for osteoarthritis of the knee joint that provides high interobserver and intraoberver agreement and that does not require complicated calculation procedures.
  
  
  METHODS
  This retrospective study sample included 44 men and 65 women who underwent both MRI and plain radiography of the knee at our institution. All patients were older than 50 years of age (mean 57.7) and had clinically suspected osteoarthritis of the knee. The standard of 4 grades on the MR grade scale was based mainly on cartilage injury and additional findings. Kellgren-Lawrence grades were assessed for the same patient group. The relationship between the results was determined. Statistical analyses were performed including kappa statistics, categorical regression analysis and nonparametric correlation analysis.
  
  
  RESULTS
  The interobserver and intraoberver agreements between the two readers in the grading of osteoarthritis were found to be almost perfect. Interobserver and intraobserver agreements were slightly lower for the MR grading system than for the Kellgren-Lawrence grading scale. The correlation between the MR grade and Kellgren-Lawrence grade was very high and did not differ with patient age. The MR grades were highly correlated with the Kellgren-Lawrence grades and showed excellent interobserver and intraobserver agreements.
  
  
  CONCLUSIONS
  This new MR grading system for osteoarthritis of the knee joint is reproducible and may be helpful for the grading of osteoarthritis of the knee without requiring reference to plain radiography.
authors.affiliation: Department of Radiology, Sungkyunkwan University School of Medicine, Kangbuk Samsung Hospital, #108 Pyung-dong, Jongno-gu, Seoul 110-746, Republic of Korea. parkhiji@gmail.com
authors.forename: Hee-Jin
authors.initials: HJ
authors.lastname: Park
authors.forename: Sam Soo
authors.initials: SS
authors.lastname: Kim
authors.forename: So-Yeon
authors.initials: SY
authors.lastname: Lee
authors.forename: Noh-Hyuck
authors.initials: NH
authors.lastname: Park
authors.forename: Ji-Yeon
authors.initials: JY
authors.lastname: Park
authors.forename: Yoon-Jung
authors.initials: YJ
authors.lastname: Choi
authors.forename: Hyun-Jun
authors.initials: HJ
authors.lastname: Jeon
mesh_terms: D000465:Algorithms; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D020370:Osteoarthritis, Knee / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*