Bilateral congenital absence of the anterior cruciate ligament associated with the absence of the medial meniscus is reported in a 34-year-old-woman. The simultaneous absence may be explained by a common embryological mesenchymal origin of the anterior cruciate ligament and the menisci. This absence was at the origin of an abnormal development of the condyles and especially of the tibial epiphysis which was tipped over in flexum. Treatment consisted of a central ligamentous plasty associated with a lateral plasty, a medial plasty and a closing anterior tibial osteotomy. The result was good.