A preclinical method for evaluating the kinematics of knee prostheses

The primary intent of anatomical knee implants is to replicate the motions of a normal knee joint. In developing such designs, a preclinical evaluation of kinematic behavior is needed. This study introduces an in vitro testing method for recording movements of the knee joint. A novel testing jig was developed and incorporated into a knee simulator setup alongside a motion capture system to directly track the medial and lateral movements of a knee prosthesis. The test system developed in this study required a number of factors to be validated; (i) gait inputs to the knee simulator (result: 0.37–1.575% error), (ii) validity of global coordinate system in the motion capture system, (iii) the position of flexion facet centers (FFCs) detected by the motion capture system (result: a maximum error of 0.08 mm in AP direction and 0.3 mm in SI direction), (iv) local coordinate system in the motion capture system (result: 1.09% error for the measurement of flexion angle), (v) that FFC results were in good agreement with inputs. In conclusion, the system developed in this study for recording FFC is a direct and reliable in vitro test method for analyzing the kinematics of a knee prosthesis.