Accuracy of T2-weighted fast spin-echo MR imaging with fat saturation in detecting cartilage defects in the knee: Comparison with arthroscopy in 130 patients

OBJECTIVE. The purpose of this study was to assess the accuracy of routine T2-weighted MR imaging in detecting and grading articular cartilage lesions in the knee compared with arthroscopy. SUBJECTS AND METHODS. We examined 130 consecutive patients who underwent MR imaging and arthroscopy of the knee for suspected internal derangement. MR imaging consisted of axial and coronal T2-weighted fast spin-echo sequence s with fat saturation and sagittal T2-weighted spin-echo sequences. Each si ngle plane was evaluated and graded for the presence and appearance of arti cular cartilage defects using a standard arthroscopic grading scheme adapte d to MR imaging. RESULTS. Of the 86 arthroscopically proven abnormalities, 81 were detected on MR imaging. Sensitivity of the T2-weighted fast spin-echo sequence with fat saturation was 61% for the coronal plane alone and 59% for the axial pl ane alone. Specificity for each plane was 99%. Sensitivity for the sagittal T2-weighted spin-echo sequence was 40%, and specificity was 100%. Sensitiv ity of the combination of axial and coronal T2-weighted fast spin-echo sequ ences with fat saturation and sagittal T2-weighted spin-echo sequence compa red with arthroscopy for revealing cartilage lesions was 94%, specificity w as 99%, and accuracy was 98%. Sensitivity of coronal and axial T2-weighted fast spin-echo sequences with fat saturation was 93%, and specificity was 9 9%. Fifty-five lesions (64%) were identically graded on MR imaging and arth roscopy. Seventy-eight lesions (90%) were within one grade using MR imaging and arthroscopy, and 84 lesions (97%) were within two grades using MR imag ing and arthroscopy. CONCLUSION. T2-weighted fast spin-echo MR imaging with fat saturation is an accurate and fast technique for detecting and grading articular cartilage defects in the knee. The combination of the axial and coronal planes offers sufficient coverage of articular surfaces to provide a high sensitivity an d specificity for chondral defects.