Symptomatic ring-shaped lateral meniscus: magnetic resonance imaging and arthroscopy.

A ring-shaped lateral meniscus is a very rare entity within the spectrum of abnormalities of lateral meniscus. We present the second case in the literature of a symptomatic ring-shaped lateral meniscus in combination with a meniscal cyst and in association with an osteochondritis dissecans lesion of the medial femoral condyle. A potential pitfall of magnetic resonance imaging (i.e., displaced meniscal tear) is addressed in the diagnosis of this entity, as well as the role of magnetic resonance imaging in revealing associated abnormalities.