Geometry And Kinematics Of Human Knee Joint

Abstract

At first glance, the human knee can look like a simple rotational joint but the real knee has more complex geometry and kinematics. Kinematics of the human knee depends on its geometry and applied analysis showed that it is a rolling joint, where the upper part of tibia rolling on femur lower end. Such kind of motion can be simply explained with rolling curves generation. In the simplest case, circle rotates on a flat surface and each point on circle circumference will generate one cycloid. Curves defined through this method highly depend on the shape of the rolling object and shape of the surface where the object roles. In the literature complex, geometry and movement of the human knee can be solved with a relatively complex mechanism that can reproduce real movement or simply by replacing knee with one rotational joint. Application of the new popular technologies (3D printing, CAD) and new approaches of mechanisms design (where the mechanism is produced as one part, and its geometrical shape allows relative movement through elastics deformation), can simplify the overall geometry and kinematic of an artificial knee joint. This will further simplify manufacturing processes, lower costs of the knee and leg prosthetics, and increase its durability by reducing the number of movable parts.