Abstract: Technology is described to provide a foot and ankle prosthesis for individuals with lower limb loss. This technology is able to store and release energy and individuals or patients who are using the foot/ankle prosthesis may be able to expend less energy when walking. The system includes a hydraulic damper attached to dynamic energy storing spring elements. The axis of rotation of the system can be near to that of an intact human ankle, providing biomimetic function. The system can utilize spring elements based on the vertical displacement of the center of pressure of an intact normal foot. A hydraulic system can provide user adjustable heel height and adaptation to inclines. The dorsiflexion and plantar flexion resistances can be independently adjusted manually or electrically. In addition, the system can be automatically locked in dorsiflexion when loaded and unlock when unloaded.