Congenital absence of the cruciate ligament is a rare condition with a prevalence of 0.017 per 1000 live births. This study reports a case of congenital absence of the anterior and posterior cruciate ligaments of the left knee associated to a type 1A fibular hemimelia, and a contribution to the existing hypotheses on knee ligaments development. According to medical literature the anomaly begins to develop around the seventh-eighth week of pregnancy. Patients with a cruciate ligament agenesis will often need a knee replacement at one point in their lives.