The proximal metaphyseal fracture of the tibia in children must be regarded as an important injury, which will be developing into a progressive crus valgum if it stays untreated. The cause of this misgrowth is the interposition of the Pes anserinus into the crack of the fracture. Initial the x-ray will show an exactly position of the tibia, so that the treatment seems to be conservative. The misgrowth only can be prevented by an operation with releasing the Pes anserinus out of the fracture. One case of this rare injury is demonstrated.