An artificial joint with two degrees of freedom has two rotary motors that move the joint in one degree of freedom when operated in respective senses of rotation and move the joint in the other degree of freedom when one of the motors is reversed. The movement depends on balancing the operation of the motors, which are controlled by a microprocessor. Sensors on the joint are connected to the microprocessor in a closed-loop feedback. A prosthetic device includes a tendon received in one end of a slot in a movable member, whereby movement of the tendon moves the movable member. A prosthesis has two parts moveable relative to one another, an actuator, and a user control. A transducer connected to the control and the actuator provides signals indicating movement effected by the actuator. A prosthesis cover includes a silicone laminate and a reinforcing liner.