What is the difference between hydraulic, pneumatic and myoelectric prostheses? What is the principle?

Hydraulic pressure and pneumatic pressure refer to the knee joint of artificial limb, which adds pneumatic pressure or hydraulic power on the basis of mechanical joint.

Electromyographic prosthesis: refers to the control unit of upper limb prosthesis, including forearm elbow amputation and upper arm shoulder amputation prosthesis. The differential amplifier on the prosthesis collects the EMG signal of the residual limb, and controls the opening and closing of the hand, the flexion and extension of the wrist joint, the flexion and extension of the elbow joint and so on through the processing chip!