Characterizing the motion of total knee replacements in laboratory tests.

The purposes of determining the motion of a total knee replacement in vitro are to characterize the stability and laxity characteristics and to predict the kinematic behavior of the total knee replacement when implanted. With this information, different total knee replacement designs can be compared, the stability of the implanted knee replacement with and without the retention of ligaments can be assessed, and tests can be formulated to measure the wear and deformation of the materials, the strength of the components, and the fixation to the bone. Initially, different ways are described for characterizing the kinematics of the natural knee. We propose a rationale for the kinematic testing of total knee replacements in vitro using mechanical tests. One of the key questions is whether there is an objective method of measuring the kinematics of a total knee replacement in vitro, which will relate to or predict its behavior in vivo.