M23.0 - Cystic meniscus
M23.02 - Cystic meniscus, posterior horn of medial meniscus
M23.021 - Cystic meniscus, posterior horn of medial meniscus, right knee
M23.022 - Cystic meniscus, posterior horn of medial meniscus, left knee
M23.029 - Cystic meniscus, posterior horn of medial meniscus, unspecified knee