Magnetic resonance imaging in the evaluation of knee injuries

To better define the role of magnetic resonance imaging (MRI) in the evaluation of knee injuries, we analyzed 10 recently published articles comparing MRI and arthroscopy in the detection of meniscal and anterior cruciate ligament tears. Sensitivity (SN), specificity (SP), positive predictive value (PPV), and negative predictive value (NPV) for medial meniscus (MM) tears, lateral meniscus (LM) tears, and anterior cruciate ligament (ACL) tears were either obtained or calculated from data contained in each article. The medians of measurements for MM tears were 97% SN, 89% SP, 88% PPV, and 96% NPV. Measurement medians for LM tears were 85% SN, 94% SP, 86% PPV, and 95% NPV. ACL tear measurement medians were 100% SN, 96% SP, 80% PPV, and 98% NPV. High NPVs were found in several studies, many of which were 100%. The high NPV of MR imaging suggests that diagnostic arthroscopic surgery is not necessary in the evaluation of patients with negative MRI studies. The superior sensitivity of MRI in detecting frank posterior horn tears, intrasubstance meniscal tears, and significant incidental findings also suggests that screening MRI scans can facilitate preoperative planning.