Bilateral congenital separation of the lateral meniscus. A case report.

Reports of congenital abnormalities of the lateral meniscus include discoid meniscus, accessory meniscus, double-layered meniscus and ring-shaped meniscus. We present a rare case of an unusual abnormality of the bilateral lateral meniscus, which was completely separated and duplicated at the midportion, although different from an accessory meniscus, with an anomaly of the anterior horn of the medial meniscus as well as a double-layered medial meniscus. This type of abnormality of the lateral meniscus and double-layered medial meniscus has not previously been described in the literature. We have designated the abnormality of the bilateral lateral meniscus a separated meniscus.