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

In an above knee prosthesis (AKP) for use by a human user, said AKP having upper and lower leg segments, a knee joint connecting the segments and a foot attached to the lower segment, the improvement comprising:

• a hydraulic damper means, pivotally connected with the leg segments for separately and variably damping each of flexion and extension rotational movements of the knee joint throughout the stance and swing phases of gait utilizing restriction of hydraulic fluid flow;
• said damper means comprising a cylinder, forming an internal chamber, and a piston adapted to slide therein, said piston engaging the cylinder in sealed relationship and dividing the chamber into first and second end chambers filled with hydraulic fluid when in use, said piston being operative to reciprocate within the cylinder chamber as the leg segments move together in flexion or separate in extension,
• said damper means having first and second passageways, each connecting the end chambers,
• said damper means having first variable valve means associated with the first passageway for regulating fluid flow therethrough and second variable valve means associated with the second passageway for regulating fluid flow therethrough,
• said damper means having first one way check valve means for enabling fluid to flow between end chambers through the first passageway when the leg segments endeavor to separate in extension and second one way check valve means for enabling fluid to flow between end chambers through the second passageway when the leg segments endeavor to move together in flexion;
• actuating means for adjusting each of the first and second variable valve means so the flow capacity of each of the first and second passageways may be separately varied;
• electronic sensing means for continuously monitoring AKP knee angle and emitting signals representative thereof,
• electronic sensing means for continuously monitoring position of the center of gravity of the user's body relative to the AKP foot and emitting signals representative thereof;
• and
• programmed computer means for receiving the emitted signals, continuously establishing from said signals the state of the AKP throughout the course of gait and activating the actuating means to separately vary the flow capacity of one or both passageways at appropriate transition points between AKP states throughout the stance and swing phases of gait.