By designing an orthosis as a system comprising a relatively rigid sole (2) with flexible regions (11a-11e) extending across the sole (2), it will be possible to dimension it to control the movements of the foot (8) during walking.It will be possible to ease the dorsal lift by providing the connecting member (7) between the sole (2) and the ankle cuff (1) with straps (4) of an elastic material, thereby obtaining an auxiliary force when the springy effect in the material is released in the dorsal lift.This results in an improved walking motion as the sole supports the foot which is also assisted in the dorsal lift.