The dorsal dislocation inferior radio-ulnar joint was treated by the shortening operation of the pronator quadratus muscle by moving the muscle origin to its dorsum, so that the pronator quadratus muscle was always under tension whether the muscle was contracted or relaxed. Thus the anatomic position and stress distribution were improved. We had treated 11 patients in the past four years.The patients were followed from four months to four and half years and the results were 9 patients excellent and 2 good.