We report a case of a 56-year-old women with severe unilateral osteoarthritis and translation due to congenital aplasia of both cruciate ligaments, which was found during knee arthroplasty surgery. Cruciate ligament insufficiency is a known risk factor in osteoarthritis but is very rarely caused by congenital aplasia and is most often due to trauma. While the patient had several common risk factors for the development of osteoarthritis the congenital aplasia may have contributed significantly in this case of osteoarthritis.