Accuracy of standard magnetic resonance imaging sequences for meniscal and chondral lesions versus knee arthroscopy. A prospective case-controlled study of 719 cases

Background: Magnetic resonance imaging (MRI) is commonly used for diagnosis and as a research tool, but its accuracy is questionable. The goal of this study was to compare the accuracy of knee MRI with clinical assessment for diagnosing meniscal tears, and to determine the accuracy of MRI for grading chondral lesions, relative to arthroscopy. Methods: Physically active patients presenting with mechanical symptoms warranting a knee arthroscopy and satisfying the inclusion criteria, had both a knee arthroscopy and MRI performed. Arthroscopic findings were compared with those of MRI, using the International Chondral Research Society grading for chondral damage, and the presence or absence of a meniscal tear. Results: A total of 719 patients were recruited over a period of 6.5 years, average age 52 years (standard deviation, SD 5.2), male:female = 493:226. Kappa scores with standard errors (SE) for agreement between MRI and knee arthroscopy were 0.41 (SE 0.1) for medial meniscal tears, and 0.44 (SE 0.1) for lateral meniscal tears. For the grade of chondral damage, the Kappa scores with SE values were 0.09 (0.1), 0.17 (0.1), and 0.22 (0.07) for anterior, medial and lateral compartments, respectively. Using areas under the receiver operating characteristic curves, we found clinical assessment was more accurate than MRI for diagnosis of lateral meniscal tears (P < 0.001), and of similar accuracy for the diagnosis of medial meniscal tears (P = 0.12). Conclusions: MRI has relatively poor correlation with arthroscopic findings for grading the chondral damage and was less accurate than clinical assessment for the diagnosis of lateral meniscal tears.