Bilateral solid parameniscal masses in the knees.

Parameniscal cysts of the knee joint are usually considered to be minor asymptomatic lesions associated with meniscal injury. We report on a rare case of bilateral knee masses in the medial soft tissues that resembled parameniscal cysts in terms of location and structure. The patient was an 80-year-old woman with severe osteoarthritis. Arthroscopy detected no meniscal tears in either knee. Arthrotomy with regional excision of the masses was required. The solid masses showed a capsular outer layer that contained fibrin deposits, granulation tissue, and fibrous cartilage fragments from the meniscus. We hypothesize that these unusual masses represent senescent or "ancient" meniscal cysts, the result of long-term fibrous degeneration of previous parameniscal cysts, and may co-occur with severe osteoarthritis and meniscal degeneration.