Knee joint loading patterns during activities of daily living in TKR patients

The kinetics and kinematics of the knee joint during a variety of activities of daily living were studied in a group of total knee replacement (TKR) patients. The parameters examined were those needed to program a force-controlled knee simulator (axial and anterior-posterior (AP) forces, internal-external (IE) moment, and flexion angle). These parameters were calculated for walking, fast walking, stand-to-sit, sit-to-stand, bending, stair ascent and stair descent using body-fixed inertial sensors, a force platform, and estimates of muscle forces. Peak values for loading patterns were not significantly different from those for an age-matched control group. Axial forces were lower in comparison to published results for normal and TKR populations, due to slower cadences and conservative estimates of muscle forces. Peak posterior forces and IE moments were higher than published results. These patterns were combined to form a spectrum loading pattern, with the activities occurring in approximately the same ratios of relative frequency as reported in the literature. The spectrum pattern can be used to program a force-controlled knee simulator in order to apply more relevant loading patterns to knee implants.