Abstract
Hypoplasia of the meniscus is a very rare congenital abnormality, with only a few cases reported to date. A 9-year-old girl visited our hospital due to lateral knee pain following a hyperextension injury to the left knee. Magnetic resonance imaging showed hypoplasia of the medial and lateral menisci, as well as a posterior horn tear of the lateral meniscus, in both knee joints. To our knowledge, this is the first report of a patient with hypoplasia of the medial and lateral menisci in both knee joints.