A prosthesis comprising at least two parts which are moveable relative to one another, an actuator connected to move one of the parts relative to the other, and a control connected to operate the actuator in dependence upon a signal issued to the control by the user. A movement transducer is connected to the control, and also to the actuator to provide signals to the control indicative of the amount of movement effected by the actuator, and the control operates the actuator in dependence upon the signals it receives from the transducer.Also, a prosthetic device comprising a tendon having a portion which engages a movable member of the device, so that movement of the tendon in a given direction urges the said movable member correspondingly. The said portion engages the said movable member by being received in one end of a slot within the movable member. The slot extends from the said end in a direction opposite to the said given direction.
