Abstract: A knee orthosis is disclosed providing forces approximating the forces exerted by predetermined knee ligaments; and which further protects against hyperextension, more specifically, the knee orthosis of the present invention provides a hinge having three members extending from a central portion, two extending upwardly and attached to the leg above the knee and one member extending downwardly and attached to the leg below the knee. During the last 15.degree. to 45.degree. of extension, the hinge, through these three members, exerts an increasing force to the anterior of the tibia proximate to the knee, so that during these critical angles of rotation the tibia may be maintained in its proper position with respect to the femur.