An unusual meniscal ganglion cyst that triggered recurrent hemarthrosis of the knee.

A 58-year-old woman suffered spontaneous recurrent hemarthrosis of the knee. In the clinical course, pigmented villonodular synovitis was mostly suspected, but in arthroscopic surgery the lateral meniscus appeared to be upturned and stuck into the lateral pouch with the meniscal ganglion cyst. It was suggested that meniscal tear with meniscal ganglion cyst was related with recurrent hemarthrosis. Generally, both the meniscal ganglion cysts and spontaneous recurrent hemarthrosis are highly rare conditions. In this case, we speculated that a negligible power could induce the meniscal tear with recurrent hemarthrosis in the particular situation in which the meniscal ganglion cyst existed. In other words, the meniscal ganglion cyst might basically and physically relate with hemorrhagic condition. Arthroscopically, the meniscal ganglion cyst was removed together with the anterior segment of the lateral meniscus. Recurrent hemarthrosis was treated successfully by resection of the meniscus.