The Silicon Ankle Foot Orthosis (SAFO) is a totally new, dynamic and elastic orthosis for treating peroneal paralysis-type ankle defects. The orthosis aids dorsiflexion during the gait cycle. A silicon reinforcement on the dorsal side provides the necessary rigidity. Upon heel strike the design allows shock absorbtion. During swing phase the SAFO supports the foot preventing the toes from dropping or catching. SAFO can be worn indoors without a shoe and it can also be worn for swimming/showering. The orthosis can be opened and fastened by velcro vulcanized in the silicon on the back of the orthosis.