The vast majority of discoid menisci are lateral. A medial discoid meniscus is very rare. A 33-year-old and a 15-year-old male patient were diagnosed as having a complete medial discoid meniscus by means of magnetic resonance imaging and arthroscopic procedures. The first patient had a peripheral tear along with cystic degeneration, and the second had a horizontal tear. One was treated successfully by an arthroscopic partial meniscectomy with a peripheral repair, and the other by an arthroscopic partial meniscectomy. We report two cases of medial discoid meniscus with a brief review of literature.