Genu recurvatum has commonly treated by Ilizarov devices, and treatment with an orthosis has rarely been reported. A 54 month old girl visited our hospital because of left knee hyperextension. The overall imbalance of the quadriceps with the hamstring muscles created 25 degrees of hyperextension. So we applied a knee-ankle-foot orthosis (KAFO) for treatment. After six months, the plain radiograph show 2 degrees hyperextension and stabilization of the knee. Genu recurvatum can be treated with an orthosis in a patient with imbalanced quadriceps and a hamstring muscle problem.