MR-IMAGING OF KNEES HAVING ISOLATED AND COMBINED LIGAMENT INJURIES

OBJECTIVE. Although clinical evaluation and MR imaging both accurately reveal injuries in knees with isolated ligament tears, physical exami nation becomes progressively less reliable when multiple lesions exist . We investigated the accuracy of MR imaging of knees having varying d egrees and numbers of ligament injuries. SUBJECTS AND METHODS. We pros pectively interpreted the MR images of 340 consecutive injured knees a nd compared these interpretations with the results of subsequent arthr oscopy or open surgery, which served as the gold standard. Our interpr etations of MR images focused on five soft-tissue supporting structure s (the two cruciate ligaments, the two collateral ligaments, and the p atellar tendon) and the two menisci. Patients were divided into three groups: no ligament injuries, single ligament injuries, and multiple l igament injuries. RESULTS. Using MR imaging, we found overall sensitiv ity and specificity for diagnosing Ligament tears to be 94% and 99%, r espectively, when no or one ligament was torn and 88% and 84%, respect ively, when two or more supporting structures were torn. The differenc e in specificity was statistically significant (p < .0001). Sensitivit y for diagnosing meniscal tears decreased as the number of injured str uctures increased, but the relationship achieved statistical significa nce (p = .001) only fbr the medial meniscus. For all categories of inj ury, MR imaging was more accurate than clinical evaluation, statistics for which were taken from the orthopedic literature. CONCLUSION. In k nees with multiple ligament injuries, the diagnostic specificity of MR imaging for ligament tears decreases, as does the sensitivity for med ial meniscal tears.