Magnetic resonance imaging of knee disorders. Clinical value and cost-effectiveness in a sports medicine practice.

To prospectively evaluate the clinical value of magnetic resonance imaging of the knee in a referral sports medicine practice, we performed a three-part study. First, we asked 72 consecutive patients a series of clinically relevant questions regarding the ordering of their magnetic resonance imaging scans. Second, we asked the treating physicians at our center if the magnetic resonance imaging findings changed the diagnosis or treatment. Third, we compared the clinical evaluation with the findings on magnetic resonance imaging scans for 37 patients who had arthroscopic confirmation. From the physician's perspective, in only three cases would the results of the scan have changed the diagnosis. Information from the scans was judged to contribute to patient treatment in only 14 of 72 patients. Finally, comparison of clinical evaluation and magnetic resonance imaging findings with findings during arthroscopic procedures showed that clinical evaluation had a sensitivity and specificity of 100% for diagnosis of anterior cruciate ligament injuries, whereas magnetic resonance imaging was 95% sensitive and 88% specific. For isolated meniscal lesions, the clinical assessment had a sensitivity and specificity of 91% compared with 82% and 87%, respectively, for magnetic resonance imaging. For evaluation of articular surface damage, the predictive value of a positive test was 100% for clinical assessment and 33% for the magnetic resonance imaging. We conclude that magnetic resonance imaging is overused in the evaluation of knee disorders and not a cost-effective method for evaluating injuries when compared with a skilled examiner. Clinical assessment equals or surpasses the magnetic resonance imaging in accuracy.