THE EFFECT OF FOOT ORTHOTICS ON 3-DIMENSIONAL KINEMATICS OF THE LEG AND REARFOOT DURING RUNNING

Foot orthotics have been used successfully in the treatment of musculo skeletal symptoms associated with structural variations of the foot. T heir effectiveness has been primarily addressed through two-dimensiona l, frontal plane motion studies of the subtalar joint in individuals c onsidered ''clinical pronators.'' Recent evidence suggests that assess ment of tibial axial rotation in combination with frontal plane analys is of calcaneal inversion/eversion may provide improved understanding of subtalar joint function. The purpose of this study was to examine t he effects of semi-rigid foot orthotics on three-dimensional lower lim b kinematics in 20 recreational runners presenting with distinct struc tural foot characteristics. Radiographic measurements were used to cla ssify subjects into a low or high rearfoot profile group. The results of the kinematic analysis showed a significant orthotic effect for rot ations occurring from heel contact to peak tibial internal rotation, a s well as in the coupling relationship between tibial axial rotation a nd calcaneal inversion/eversion. Both groups responded similarly with a mean reduction of 2 degrees in tibial internal relation. No differen ces were found for the frontal plane rotations for either group when o rthotics were worn. The findings suggest that the maximum effect of or thotics may be realized in the first 50% of stance and related to the changes in tibial axial relation.