US Patent 8986398 Hydraulic prosthetic ankle

A range of motion (ROM) prosthetic foot and passive dampening ankle joint have limited dorsiflexion-plantarflexion (up and down) pivoting to accommodate different environments, and a spring to provide resilient resistance to plantarflexion (or lowering of the toe), and to bias the foot in dorsiflexion (or raising the toe). The ankle joint has a rear pivot rearward of a hydraulic link for a smooth feel. The ankle joint has an internal bumper in a hydraulic cylinder for a smooth feel. The ankle joint has an internal hydraulic compensator disposed in the cylinder and carried by the piston to equalize volume.