The accuracy of magnetic resonance imaging in diagnosing chronic posterior cruciate ligament injury.

Magnetic resonance imaging (MRI) is widely believed to be highly accurate in diagnosing injuries of the posterior cruciate ligament (PCL). The aim of this study was to determine the accuracy of MRI in diagnosing chronic PCL injury. MRI was performed on 10 knees with a clinical and arthroscopic diagnosis of a PCL injury sustained at least 6 months previously. Seven experienced musculoskeletal radiologists subsequently reviewed the scans. Their accuracy in diagnosing a PCL injury was 57% (40-80%). Thus, although MRI may be reliable in diagnosing acute PCL injury, MRI is not so reliable in evaluating chronic injuries. We postulate that, in the case of a chronic PCL injury, healing in continuity may occur, producing an intact but lax ligament. As demonstrated by our study, MRI may then be less accurate. This should be borne in mind when assessing the MRI scans of a suspected chronic PCL injury.