A brace for augmenting extension of a user's limb about a joint comprises an upper arm pivotably attached to a lower arm. At least one compression element is attached to at least one of the upper and lower arms, and a substantially inelastic tensioning element is affixed to the other of the upper and lower arms over at least one tensioning member. Applying a force to bend the brace to a flexed position loads the compression element, and upon removal of the flexing force the compression element applies a restoring force to urge the brace back to the extended position. The compression element may comprise a hydraulic tension spring comprising at least one cylinder having a sealed portion defining a liquid containment space, and a piston comprising a compressing portion having a smaller diameter than the cylinder and extending axially through a hydraulic seal into the liquid containment space. A guide for maintaining the piston oriented axially relative to the frame maintains piston alignment so that when the frame is fixed in place and tension is applied to the tensioning member, the compressing portion of the piston rod intrudes further into the liquid containment space, compressing the hydraulic fluid and loading the spring.
