A method and an apparatus for enhancing operation of a leg prothesis is provided. The apparatus includes a variable stiffness module configured to be attached between a first portion and a second portion of a leg prothesis. The first portion is configured to move relative to the second portion in a first plane during a first gait phase. The variable stiffness module defines an interior region configured to store pressurized fluid. A motor is configured to reduce a volume of the interior region during a second gait phase to increased an amount of stored energy of the pressurized fluid. The amount of stored energy is released during a third gait phase to assist a subject wearing the leg prothesis during the third gait phase.