Abstract: The D-DAFO (DeRoos-Dynamic Ankle Foot Orthosis) invention is a dynamic support system designed to maintain the correct alignment of the bones in the foot and ankle. The D-DAFO's dynamic stability allows the patient's tibia to rotate forward anteriorly and yet supported, while continuously providing the support to hold the patient in sub-talar neutral, and/or improved alignment for function, while simultaneously maintaining tone and extension synergy.