MR imaging of the knee menisci

MR imaging of the knee is highly accurate for the noninvasive diagnosis of meniscal tears and other meniscal pathology. Familiarity with the normal anatomy and common pitfalls reduces errant interpretations, but does not eliminate them entirely. The two MR imaging signs of a meniscal tear are abnormal intrameniscal signal on a short-TE image that unequivocally contacts the meniscal surface, and abnormal meniscal morphology in the absence of prior meniscal surgery. To help guide the treatment of meniscal injuries, which continues to evolve, the MR imaging report should thoroughly describe tears, and not simply indicate whether a meniscal tear is present. In the patient with an ACL tear, the accuracy of MR imaging examination for meniscal tears, especially lateral tears, diminishes but still surpasses that of physical examination. The MR imaging criteria for meniscal tears need to be modified in patients who have undergone meniscal surgery.