Negative MRI findings in knee injury: clinical implications

Magnetic resonance imaging (MRI) is now commonly used to diagnose knee pathology. Based on results in a study conducted in a private practice setting, the diagnostic value of MRI for all articular cartilage surfaces, menisci, ligaments, and soft tissue structures of the knee was determined. Subjects included 102 consecutive patients undergoing arthroscopic knee surgery for whom MRI findings also were available. Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of MRI were calculated. Sensitivity was highest for meniscus tears: 73.2% for medial tears and 63.3% for lateral tears. Sensitivity for other pathologies was poor, ranging from 26.2% for chondromalacia of the patella to 11.1% for loose bodies. Negative predictive values were variable, ranging from 84.3% for lateral meniscus tears to 39.2% for chondromalacia of the patella. MRI for most pathologies had an NPV between 50 and 75%. Results indicate a high rate of false negative MRI findings.