Bilateral discoid medial menisci.

This article adds 2 more cases of bilateral discoid medial menisci to the previously reported 9 cases. The radiographs of the first case revealed bilateral cupping of the medial tibial plateaus and a small lytic lesion of the left distal medial femoral metaphysis. Beside the posteriorly unstable incomplete type discoid medial meniscus, the left knee had several associated arthroscopic findings: depression of the medial tibial plateau with exposed subchondral bone, anomalous insertion of the anterior horn of the discoid meniscus to the anterior cruciate ligament, a pathological medial plica, and longitudinal deep fissures in the trochlea. The second case was a complete type with peripheral horizontal cleavage tears. Following arthroscopic surgery, magnetic resonance imaging (MRI) scans of the contralateral knees were obtained in both cases to search for bilaterality. MRI revealed discoid medial menisci in the unoperated knees as well. The short-term results of arthroscopic meniscectomy may not be as satisfactory as those reported for normal menisci.