Bilateral Congenital Absence of the Anterior Cruciate Ligaments in an Adolescent Male: A Rare Clinical Presentation and Review

A 16-year-old male presented with bilateral knee instability and intermittent pain without any history of trauma or surgery. Clinical examination revealed positive Lachman and anterior drawer tests bilaterally. Magnetic resonance imaging demonstrated complete bilateral absence of the anterior cruciate ligaments (ACLs) with associated thickening of the posterior cruciate ligaments. No meniscal abnormalities were found. However, this was associated with lateral femoral condylar hypoplasia, a shallow femoral notch, and lateral tibial spine hypoplasia bilaterally. Congenital absence of the ACL is an extremely rare condition, particularly when bilateral. It is often underdiagnosed in asymptomatic individuals until adolescence. Recognition is important to avoid misdiagnosis as traumatic ACL injury. Management is symptom-dependent, with conservative treatment preferred for mild cases. Surgical reconstruction may be considered for persistent instability. This case underscores the importance of including congenital anomalies in the differential diagnosis of nontraumatic knee instability in adolescents.