BACKGROUND: The scientific evidence behind the mechanical function of foot orthoses is still controversial. Research studies that have investigated the kinematic effect of foot orthoses on the lower extremity have shown variable results, with orthoses causing either no significant change or a small significant change in foot kinematics. METHODS: The right limbs of 12 healthy asymptomatic individuals were studied in three walking conditions: barefoot, with a 7 degrees rearfoot varus wedge, and with a 7 degrees rearfoot valgus wedge. Kinematic and kinetic variables measured were the foot progression angle, the peak internal tibial rotation angle, and net ankle inversion moments during the stance phase in the three conditions. RESULTS: There were statistically significant differences in the foot progression angle between the barefoot and varus wedge conditions and between the varus and valgus wedge conditions. There were no significant changes in peak internal tibial rotation among the three conditions tested. However, rearfoot varus wedges significantly reduced net ankle inversion moments compared with barefoot and rearfoot valgus wedges. CONCLUSIONS: These results support the idea that foot orthoses work by methods other than by changing kinematic parameters. The present study supports the concept that foot orthoses work primarily by altering kinetics, with their effects on kinematics being secondary.
BACKGROUND: The scientific evidence behind the mechanical function of foot orthoses is still controversial. Research studies that have investigated the kinematic effect of foot orthoses on the lower extremity have shown variable results, with orthoses causing either no significant change or a small significant change in foot kinematics. METHODS: The right limbs of 12 healthy asymptomatic individuals were studied in three walking conditions: barefoot, with a 7 degrees rearfoot varus wedge, and with a 7 degrees rearfoot valgus wedge. Kinematic and kinetic variables measured were the foot progression angle, the peak internal tibial rotation angle, and net ankle inversion moments during the stance phase in the three conditions. RESULTS: There were statistically significant differences in the foot progression angle between the barefoot and varus wedge conditions and between the varus and valgus wedge conditions. There were no significant changes in peak internal tibial rotation among the three conditions tested. However, rearfoot varus wedges significantly reduced net ankle inversion moments compared with barefoot and rearfoot valgus wedges. CONCLUSIONS: These results support the idea that foot orthoses work by methods other than by changing kinematic parameters. The present study supports the concept that foot orthoses work primarily by altering kinetics, with their effects on kinematics being secondary.