Discoid meniscus associated with agenesis of the anterior cruciate ligament in an 8-year-old child.

Among the congenital anomalies involving the lateral compartment of the knee, the combination of both a discoid meniscus and agenesis of the anterior cruciate ligament (ACL) is extremely rare and probably underestimated due to the presence of a meniscofemoral ligament often mistaken for an intact ACL. The therapeutic management of such abnormalities is not univocal and highly depends on their clinical impact. We report on the observations of an 8-year-old boy presenting with a cystic formation on a lateral discoid meniscus associated with agenesis of the ACL and the presence of an anterior lateral meniscofemoral ligament.