In the literature mechanical factors are considered as the most frequent etiology of Morton's disease. The pathology is a classical progressive fibrosis with rupture of nerve "fascicules" and/of arterioli, without nerve proliferation and without specific inflammatory factors. The deep intermetatarsal ligament and the bursae between the metatarsal heads are probably the most important factors in nerve irritation. In the literature there are few precise descriptions of the mechanism of irritation of the nerve, either by the bursae between the metatarsal heads, by the deep intermetatarsal ligament, or by the tendons of the lumbrical muscles which are close to the nerve. The aim of this study is an analysis of the mobility of these structures in both planes, by radiological evaluation in the erect position, after implantation of radiopaque pellets. The authors also present an hypothesis on the mechanism of the lesion.