Comparison of magnetic resonance imaging for patients with acute and chronic anterior cruciate ligament tears.

To compare the direct and indirect signs on magnetic resonance imaging (MRI) for patients with acute and chronic anterior cruciate ligament (ACL) tears.Two independent reviewers retrospectively evaluated the MRI images of 377 patients with ACL tear confirmed by arthroscopy. There were 160 cases with acute ACL tear and 217 cases with chronic ACL tear. Direct signs in T1- and T2-wighted images and indirect signs including meniscus injury, the collateral ligament injury, cartilage damage or osteoarthritis, kissing contusion, Notch syndrome and abnormal posterior cruciate ligament (PCL) and other indirect signs were evaluated.For direct signs on MRI, no significant differences were found between the acute and chronic ACL tear in prevalence of focal high signal in substance of T2-wighted images and in that of abnormal orientation, discontinuity, thickening, or focal masses in substance of T1-weighted images. However, higher incidence of diffuse high signal of T2-weighted images for acute ACL tear was found compared to that for chronic ACL tear (55.0% vs 3.2%). For indirect signs on MRI, the collateral ligament tear (20.6% vs 2.3%), cartilage damage or osteoarthritis (14.4% vs 25.8%), kissing contusion (57.4% vs 0%), Notch syndrome (28.1% vs 3.2%), and bowing type of PCL (33.1% vs 47.0%) can differentiate the acute from chronic ACL tear.Some direct and indirect signs on MRI are closely related to the acute and chronic ACL tear.