Deep flexion-oriented bisurface-type knee joint and its tibial rotation that attributes its high performance of flexion.

In 1989, we developed an artificial knee prosthesis that could accommodate the oriental lifestyle where people would sit more often on the floor than on a chair. The knee had a bisurface feature with an auxiliary joint of a ball and socket at the center of the posterior part aiming at an improved flexional function. The auxiliary joint functions not only to facilitate a rollback movement but also to add a rotational movement.