Abstract: A device for giving a set position to the lower limbs of persons required to remain in a supine position for an extended period, comprises a central block (1) which is provided with two side support surfaces (2a and 2b) for the legs of the person. The two surfaces are arranged according to two vertical planes which converge on the subject and define the angle at which his lower limbs are to be set. At least one of said side support surfaces of the central block is associated with at least one side support (5, 5') to allow the corresponding leg to rest. This support may be placed against the surface of the central block and comprises an upward-facing surface (6) with a concave profile which ensures a comfortable and stable position of the leg.