Ring-shaped lateral meniscus combined with an accessory meniscus: A rare anatomical variant

A ring-shaped meniscus is a very rare anatomical variant among all meniscal abnormalities. Additionally, an accessory meniscus is extremely rare, and only a few cases have been reported. We herein report a case involving the combination of these two features in a single lateral meniscus. These abnormalities were found during arthroscopic surgery for removal of an osteochondral fragment that had detached from the patellar bone and plication of the medial patellofemoral ligament in a patient with acute patellar dislocation. To our knowledge, each variant is extremely rare and the combination of the two variants has not been reported.