Abnormal superior popliteomeniscal fascicle and posterior pericapsular edema: indirect MR imaging signs of a lateral meniscal tear.

OBJECTIVE: Because MR diagnosis of lateral meniscal tears can be difficult, indirect signs may be useful when a tear is suspected. We studied whether an abnormality of the superior popliteomeniscal fascicle or pericapsular edema was associated with lateral meniscal tears and thus may be an indirect MR imaging sign of a lateral meniscal tear.
MATERIALS AND METHODS: We identified 59 consecutive patients who underwent both knee MR imaging examinations and knee arthroscopy. Thirty patients had lateral meniscal tears, and 29 had intact lateral menisci. We reviewed paired sagittal proton density- and T2-weighted MR images from these 59 patients for abnormal superior popliteomeniscal fascicles and edema surrounding the posterolateral capsule.
RESULTS: The superior popliteomeniscal fascicles were abnormal in nine of the 30 patients with torn lateral menisci but were normal in all 29 patients with intact menisci (p = 0.001). Abnormal fascicles were apparent only when the lateral meniscal tear involved the posterior horn. Posterior pericapsular edema was seen in 10 patients with a torn posterior horn and in one patient with an anterior horn tear of the lateral meniscus, but in only two patients with intact menisci (p = 0.006).
CONCLUSION: The presence of superior popliteomeniscal fascicle abnormalities and of posterior pericapsular edema is significantly associated with a tear of the lateral meniscus, most commonly in the posterior horn. Noting the presence of these findings may help improve the accuracy of MR diagnosis of lateral meniscal tears.