Bilateral absence of the cruciate ligaments with meniscal dysplasia: Unexpected diagnosis in a child with juvenile idiopathic arthritis.

Bilateral agenesis of the cruciate ligaments is a rare congenital anomaly. We report a unique case of a young girl who had congenital short femur and diagnosed with polyarticular juvenile idiopathic arthritis (JIA) and later discovered to have congenital absence of both anterior and posterior cruciate ligaments and meniscal dysplasia in both the knees when MRI was performed at 11 years of age. The MRI was performed to evaluate knee laxity and persistent symptoms despite medical management and multiple steroid injections for arthritis treatment. This patient is one of the youngest with congenital absence of both the cruciate ligaments to be treated with ACL reconstruction. We highlight the unique radiographic imaging manifestations of congenital cruciate ligament agenesis and emphasize the role of MRI to confirm and depict additional intraarticular abnormalities.