Magnetic Resonance Imaging of the Knee. Correlation with Arthroscopy.

161 patients, 169 knees were evaluated with magnetic resonance imaging (MRI) and arthroscopy. MR findings and arthroscopic findings agreed in 74.6% of medial menisci, 74.6% of lateral menisci, 92.3% of anterior cruciate ligaments (ACL), 95.3% of posterior cruciate ligaments (PCL). The results between JOA (the Japanese Orthopaedic Association) -authorized orthopedists and junior residents were almost similar. On the basis of arthroscopic findings, false-positive and false-nagative cases of MRI were studied. Intrameniscal signal communicating with a meniscal articular surface was an important MRI finding for meniscal tear at arthroscopy. False-positive findings at MRI of the anterior and posterior horn regions of menisci may reflect the inability to completely and accurately visualize the meniscus with arthroscopy. False-negative findings at MRI of menisci often occurred in small tears. It may be difficult to accurately evaluate the region around the popliteus tendon with MRI. False-positive findings at MRI of the ACL may result from the partial volume effect because of proliferating synovium. False-positive findings of the PCL occurred, because ACL deficiency brings the sigmoid deformity at MRI of the PCL. False-negative findings of cruciate ligaments resulted from small tears.