Abstract: A knee prosthesis system including a knee prosthesis, an actuator and a controlling unit. The knee prosthesis includes a thigh segment and a shank segment. The actuator rotatably connects the shank segment and the thigh segment. The actuator is configured to controllably assume a powered knee behavior to generate knee motion or a passive knee behavior to resist knee motion. The controlling unit includes a finite-state control structure. The controlling unit electrically communicates with the actuator. The control structure includes at least three passive states and at least one powered state. The passive states include a passive stance-resistance state, a swing-flexion state, and a swing-extension state and the at least one powered state includes at least one of a swing-assistance state, a stance-assistance state, and a powered-swing state.

Abstract: A knee prosthesis or orthosis includes at least one moveable joint and a torque modulating unit. The torque modulating unit is configured to impose a controllable torque on the at least one moveable joint. The torque modulating unit includes at least one of a motor or brake. The at least one of the motor or brake is coupled to the at least one moveable joint via an electronically-controlled transmission. The electronically-controlled transmission is a two-speed transmission.