Sliding pivot knee joint

Claim 1

A joint structure for use in knee braces and the like, comprising: upper and lower joint elements; the lower joint element having a ramp member and a pair of furcations, both of the furcations overlapping a concave edge surface of the ramp member; the upper joint element having a head which is received between the furcations for articular motion of the upper joint element relative to the lower joint element; the forward portion of the lower edge surface of the head and said concave edge surface having approximately the same radius of curvature; the upper joint element having an elongated slot formed within said head; the lower joint element having a pin passing through said slot and connecting said joint elements together, the elongated slot having lower and upper end portions adapted to engage said pin and a central portion having curved edge surfaces with approximately said radius of curvature; the central portion being dimensioned to permit said pin to slide between said slot end portions as said joint elements rotate with respect to each other at the same time the forward portion of the lower edge surface of the head engages the concave edge surface of the ramp member, the pin moving within the slot toward the upper end portion thereof as the angle between the longitudinal axes of the joint elements is increased; the joint structure being locked with respect to any further increase in the angle between the longitudinal axes of the upper and lower joint elements when the pin engages the upper end portion; the head defining a rearwardly projecting lobe, the outer edge surface of the lobe having a substantially smaller radius of curvature than does the concave edge surface of the ramp member; the lower end portion of the slot being arranged on said upper joint element so that when the pin engages, said lower end portion, the pin is positioned at approximately the center of curvature of the outer edge surface of the lobe; the pin being the center of rotation about which the joint elements can rotate as the angle between their longitudinal axes is decreased beyond a limiting angle which is attained when the pin engages the lower end portion of the slot, the limiting angle being substantially less than 180° and being within the range of angles between said longitudinal axes which are traversed as the upper and lower joint elements undergo motions which are encountered when a wearer of the joint structure is using it to approximate a normal walking gait; the upper joint element being rotatable about the pin to decrease the angle between said longitudinal axes even when the lower joint element is stationary once the angle between said longitudinal axes is less than the limiting angle, thereby facilitating a wearer's actions in sitting down; the forward portion of the lower edge surface being curved downwardly and rearwardly at approximately the same angle to the longitudinal axis of the upper joint element as is the concave edge surface to the longitudinal axis of the lower joint element, so that sliding contact is maintained between substantial sections of the forward portions of the lower edge surface and the concave edge surface when the angle between the longitudinal axes of the joint elements is greater than said limiting angle, thereby preventing an accidental rotation of the joint elements toward each other when the contiguous edge surfaces of the joint elements are not under compression.