Double-layered lateral meniscus.

A case of double-layered lateral meniscus in which an accessory proximal hemimeniscus was overlying the body and posterior horn of the lateral meniscus is here reported. The accessory hemimeniscus lays marginal and parallel to the normal lateral meniscus with its periphery dissociated from the capsule and was significantly thinner and more mobile than its underlying counterpart. It was resected arthroscopically, and the patient's symptoms were significantly improved. This case demonstrates an interesting and extremely rare anatomical abnormality of the lateral meniscus.