Lower limb prosthesis

An active ankle joint prosthesis comprising a shin member and a foot member and constructed such that the foot member is able to execute a flexion movement relative to the shin member, and an ankle flexion control system for controlling and actively driving the relative flexion movement between the shin member and the foot member, wherein the ankle flexion control system comprises:

• a hydraulic circuit interconnecting the shin member and the foot member, and comprising a piston and cylinder assembly for converting fluid flow energy in the hydraulic circuit into mechanical movement resulting in ankle flexion and for converting the mechanical movement resulting from ankle flexion into fluid flow energy in the hydraulic circuit;
• a rechargeable battery;
• a generator-motor electrical machine operable as a generator to convert the fluid flow energy in the hydraulic circuit into electrical energy for charging the rechargeable battery and as a motor to convert the electrical energy from the battery into fluid flow energy in the hydraulic circuit;
• and
• an energy input coupled to the rechargeable battery and configured to receive energy into the ankle flexion control system from an external energy source to further charge the battery from the said external energy source;
• and wherein the active ankle joint prosthesis further comprises;
• at least one sensor for sensing a kinetic or kinematic parameter of locomotion;
• and
• a processor coupled to the at least one sensor and the ankle flexion control system, and wherein the processor is configured to control both (i) fluid flow energy resulting from flexion movement arising from application of a load to the active ankle joint prosthesis and (ii) delivery of electrical energy to the generator-motor electrical machine to drive the fluid flow energy in the hydraulic circuit and consequently drive mechanical movement in the piston and cylinder assembly resulting in the flexion of the active ankle joint prosthesis at different parts of a walking gait cycle in response to signals received from the at least one sensor, such that, in a part of a stance phase following peak plantar flexion, the ankle flexion control system is configured to drive the foot member in a direction of dorsi-flexion.