System for controlling artificial knee joint action in an above knee prosthesis

A method for controlling rotation of the knee joint of an above knee prosthesis (AKP) in each of flexion and extension, said AKP in use having a predictable pattern of swing and stance phase states having durations, using hydraulic fluid pumping means, driven by the AKP, for circulating fluid, two passageways, each connected with the pumping means, for circulation of fluid therethrough, means for controlling the entry of pumped fluid into the first passageway so that it only enters when the AKP Is experiencing flexion, means for controlling the entry of pumped fluid into the second passageway so that it only enters when the AKP is experiencing extension, first variable valve means associated with the first passageway for restricting the flow capacity thereof, second variable valve means associated with the second passageway for restricting the flow capacity thereof, actuating means for adjusting each variable valve means, sensor means for measuring, during the course of AKP movement, at least two AKP characteristics which vary with the activity of the AKP, computer means connected with the sensor means and the actuating means and programmed for establishing the state of the AKP using the sensor means measurements and for controlling the actuating means to adjust the first and second variable valve means to separately vary the flow capacity of each passageway, comprising the steps of:

• (a) circulating liquid hydraulic fluid with the pumping means through the first passageway in the course of flexion and through the second passageway in the course of extension;
• (b) using the sensor means to continuously measure, throughout the course of AKP movement, at least two AKP characteristics which vary with the activity of the AKP;
• (c) transmitting the sensor means measurements to the computer means and using the measurements to continuously establish the state of the AKP throughout the course of its movement, having reference to the predictable patterns and durations of AKP movements;
• and
• (d) utilizing the computer means to separately adjust the first and second variable valve means to separately vary the flow capacity of the first passageway at pre-determined transition points in the course of AKP movement and separately vary the flow capacity of the second passageway at pre-determined transition points in the course of AKP movement, to separately and variably damp knee rotation in each of flexion and extension.