An orthopedic brace for preventing injury to a wearer including a body having a series of liquid filled regions, the body having a first more flexible state wherein the liquid filled regions contain a liquid material and a second more rigid state wherein the liquid within the regions is hardened to a second harder state, the body transformable from the first state to the second state upon receiving a force which exceeds a predetermined value. A chemical reaction or an isothermal process can cause the phase change.