Synovialisation of the torn anterior cruciate ligament of the knee: comparison between magnetic resonance and arthroscopy

The aim of this study was to assess the accuracy of MR in the diagnosis of synovialisation of the anterior cruciate ligament (ACL) compared with arthroscopy. One hundred and forty-nine patients were examined with MR imaging and arthroscopy of the knee. The MR sign used to consider a synovialised ACL consisted of hypointense fibrillar tracts, disrupted and wavily, in its expected course. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV), comparison of proportions (McNemar test) and Kappa values for agreement between MR imaging and arthroscopy were calculated. Of the 133 (89.3 %) ligaments without synovialisation at arthroscopy, 130 accorded with the MR results. Of the 16 (10.7 %) synovialised ligaments, 13 accorded with the MR results. Three false-positive and three false-negative MR diagnoses were identified. The agreement between both techniques was excellent (Kappa = 0.79; p = 0.000), without differences (McNemar test; p = 1). Sensitivity was 0.81, specificity 0.98, PPV 0.98 and NPV 0.81. Magnetic resonance imaging is highly reliability for synovialisation diagnosis. The imaging sign used to diagnose synovialised ACL (hypointense comma-like tracts in its expected course) is reliable. As this reparative process can simulate an intact ligament, knowledge of this sign is important in diagnosing synovialisation of ACL tears so as not to confuse it with normal ACL.