QUANTITATIVE MR-IMAGING EVALUATION OF CHONDROPATHY IN OSTEOARTHRITIC KNEES

PURPOSE: To determine the validity and the reliability of T1-weighted three-dimensional gradient-echo magnetic resonance (MR) imaging for qu antification of articular cartilage abnormalities of osteoarthritic kn ees. MATERIALS AND METHODS: Forty-three patients (mean age, 63 years) with knee osteoarthritis (American College of Rheumatology criteria) o f the medial tibiofemoral compartment underwent a prospective, cross-s ectional study. Knees were examined with a T1-weighted three-dimension al gradient-echo sequence (1.4-mm contiguous sections), with use of a 0.2-T dedicated MR unit, before arthroscopic exploration. The tibiofem oral articular cartilage abnormalities were quantified blindly on both the MR and arthroscopic images with the French Society of Arthroscopy (SFA) score (0-100) and grading scheme (five grades). RESULTS: There was a statistically significant correlation between the SFA-arthroscop ic score and the SFA-MR score (r = .83) and between the SFA-arthroscop ic grade and the SFA-MR grade (weighted kappa = 0.84). The deepest car tilage lesions graded with arthroscopy and MR imaging showed correlati on in the medial femoral condyle (weighted kappa = 0.83) and in the me dial tibial plateau (weighted kappa = 0.84). The intraobserver reliabi lity of the SFA-MR score was higher (r = .94) than the interobserver r eliability (r = .80). CONCLUSION: Quantification of chondropathy with MR imaging is feasible and well correlated with anatomic cartilage bre akdown.