The Accuracy of Magnetic Resonance Imaging in the Diagnosis of Meniscal and Cruciate Ligament Tears of the Knee

During the past decade, magnetic resonance imaging (MRI) has been accepted as the ideal approach for primary diagnosis of traumatic knee intra-articular lesion. Despite this, the overall diagnostic accuracy of MRI has been carefully scrutinized in Iran. The purpose of this investigation was to scrutinize the diagnostic accuracy of MRI of the knee in identifying traumatic intra-articular knee lesions. We compared MRI findings with subsequent arthroscopic findings (as the gold standard) in 107 patients (107 knees) with a clinical diagnosis of traumatic intra-articular knee lesion. The sensitivity, specificity, positive predictive value, negative predictive value, and the accuracy of MRI were calculated based on arthroscopic findings for menisci and cruciate ligaments. MRI showed the following results for medial meniscus: sensitivity 83%; specificity 37%; positive predictive value 46%; negative predictive value 77%; and accuracy 55%. For lateral meniscus it showed the following sensitivity 43%; specificity 86%; positive predictive value 40%; negative predictive value 87%; and accuracy 79%. MRI showed the following results for anterior cruciate ligament (ACL): sensitivity 62%; specificity 90%; positive predictive value 71%; negative predictive value 66%; and accuracy 75%. In addition, it showed the following results for posterior cruciate ligament (PCL): sensitivity 60%; specificity 94%; positive predictive value 42%; negative predictive value 98%; and accuracy 94%. The overall accuracy of MRI was 62.5%. We compared MRI accuracy in two time periods to investigate if there was any improvement over time. Our data showed a significant increase in the accuracy of detection of ACL injuries by MRI in more recent patients; however, there was no improvement in the diagnosis of other internal knee derangements. In addition, overall MRI accuracy was the same in patients from different age groups. We concluded that the overall accuracy of MRI in diagnosing intra-articular lesions of the knee in Iran is comparable with other published studies in the literature. However, it could be improved; if radiologists and orthopedists work together to find possible flaws, their cooperation would result in optimal use of this diagnostic modality.