Errors at knee magnetic resonance imaging: true or false?

Amongst a series of 332 patients undergoing a prospective evaluation of the influence of magnetic resonance imaging (MRI) on diagnosis and outcome, arthroscopic correlation became available in 92 knees (91 patients). The MRI report, the arthroscopic findings and the patient's case notes were reviewed by a consensus panel. With respect to the menisci and cruciate ligaments, the formal radiological report was at variance with the arthroscopic findings in 22/349 sites where there had been no previous surgery (10 medial meniscus, six lateral meniscus and six anterior cruciate ligament). 12 of these 22 errors were considered, on review, to be genuine MRI errors. However, considerable controversy remains as to whether the other 10 "errors" were true or false. There are several factors which contribute to such controversy. These include technically difficult arthroscopies, delays between MRI and arthroscopy, and ambiguities in the wording of both the referral letter and the radiological report. These factors should be considered when evaluating the diagnostic performance of both MRI and arthroscopy.