Intrameniscal cysts begin with the flow of synovial fluid from a meniscal tear in one direction, enlarging probably as a result of an on-and-off valve mechanism of the tear flap. The current available literature focuses primarily on the necessity for surgery, however a large meniscus resection to remove cysts may place an additional burden on menisci, leading ultimately to knee joint degenerative changes. In this article, we present a rare case of intrameniscal cysts with an isolated horizontal meniscal tear in an adolescent, and describe a new arthroscopic procedure for treating this type of intrameniscal cyst. We performed arthroscopic partial release of the meniscal tear check-valve mechanism, preventing further intrameniscal cyst expansion. The patient's clinical symptoms improved, and this procedure may also be useful in treating intrameniscal cysts with an isolated horizontal meniscal tear and can be considered as an option to preserve meniscal function and minimize degenerative arthritis in young athletes.