Fibrous tether at the distal femur is a rare condition that causes angular deformity of the lower extremity; only 18 cases have been reported previously. We report the case of a 2-year-old boy presenting with unilateral genu valgus. The patient had a subsequent lateral patellar dislocation, 1 year after surgical correction. A second surgery was performed to correct this patellar dislocation. Intraoperative finding indicated contracted lateral patellar retinaculum. To the best of our knowledge, this is the first report of such a finding. The natural history is still not understood. At the 6-month-follow-up visit, the patient still has good results without recurrent patellar dislocation or angular deformity. We also review the literature in terms of proper treatment and results of treatment.