Accuracy of magnetic resonance imaging in the knee

Objective: To determine the accuracy of magnetic resonance imaging (MRI) in the assessment of various knee disorders in comparison with arthroscopic findings and pathologic diagnosis. Design: A retrospective and comparative study. Place and Duration of Study: Radiology Department, Aga Khan University Hospital, Karachi, from 01-12-1996 to 30-06-2000. Patients and Methods: Fifty-six subjects (36 males and 20 females), included in this study, had abnormal findings on MRI, which were correlated with arthroscopic findings in 50 cases and pathological diagnosis in 6 cases. Plain X-rays were available in all cases. Results: The sensitivity, specificity and accuracy for MRI of the menisci and cruciate ligaments were as follows: medial meniscus pathologies 87% sensitivity, 94% specificity and 92% accuracy; lateral meniscus pathologies 92% sensitivity, 89% specificity and 90% accuracy; anterior cruciate ligament injuries 95% sensitivity, 96% specificity and 96% accuracy and posterior cruciate ligament injuries 100% sensitivity, 98% specificity and 98% accuracy. Pathological diagnosis was available in 6 cases. MR imaging suggested the diagnosis of tuberculosis and metastases as well as mapped out the extent of osteogenic sarcoma, fibromatoses and rhabdomyosarcoma. Conclusion: This study confirms that MR imaging of the knee is highly sensitive, specific, and accurate.