Introduction: congenital radioulnar synostosis is an uncommon congenital anomaly, thatcauses a limitation of the forearm supination, often bilateral. The origin of this anomaly occurs when the differentiation of the cartilaginous contour of the radius and ulna does not take place during the embryonic period. Objective:to show two congenital radioulnar sinostosis cases analyzing variable about the topic. Case report:there are two different types of synostosis. In these cases the symptoms are mild because the compensate thein limitation in pronosupinationwith hypermobility of other joints of the upper limb. X-rays of upper limbs are the diagnostic procedures. The management will be conservative, but the treatment depends on the degree of functionality of the forearm. Conclusions:proximal radioulnarsynostosis is anon frequent affection, that brings about difficulties carrying out  actions with the hands, Its diagnosis is relatively simple by means of the clinical findings andplain X-rays of  the elbow.