Congenital Absence of the Anterior Cruciate Ligament
The incidence of congenital absence of the anterior cruciate ligament (ACL) is extremely low. Congenital ACL absence has most often been found in association with conditions such as knee dislocation, knee dysplasia, proximal focal femoral deficiency, and fibular hemimelia.
We report on the incidental finding of ACL aplasia in a patient with a medial meniscal tear and history of leg-length discrepancy. As has been found in prior case studies, this patient had hypertrophy of the meniscofemoral ligament of Humphrey, which likely lent her stability. This case highlights the importance of differentiating between a stable and an unstable knee in congenital absence of the ACL.
Conclusion
This report presents a patient whose symptoms improved after resection of her medial meniscal tear. This patient will be followed long-term to delineate her clinical course and to monitor for instability and/or development of osteoarthritis. Future studies should compare the treatment of congenital absence of the ACL with reconstruction and with conservative management.
