In the present study, a human ankle joint pushing mechanism with a brace structure was developed, and the force balance relationship of the proposed system to avoid pain at sites other than the ankle joint was evaluated. The proposed system uses the brace structure to prevent the movement of the geometric arrangement of the ankle joint and the device rotational axis when pressure is applied to the foot. The results of experiments revealed that the proposed brace mechanism did not change the position of the ankle joint when a force was applied to the foot so that pain could be avoided. The proposed mechanism will be useful for developing a device for the purpose of applying large forces to the ankle joint.