Influence and benefits of foot orthoses on kinematics, kinetics and muscle activation during step descent task

Background: Medial wedged foot orthoses are frequently prescribed to reduce retropatellar stress in patients with patellofemoral pain (PFP) by controlling calcaneal eversion and internal rotation of the tibia. During activities of daily living, the highest patella loads occur during stair descent, but the effect of foot orthoses during stair descent remains unclear. Research question: The purpose of this study was to compare the kinematics, kinetics and muscle activation during a step descent task in healthy volunteers using three designs of foot orthoses (insoles). Methods: Sixteen healthy subjects with a mean age of 25.7 years, BMI of 23.3, and +5 Foot Posture Index were recruited. Subjects performed a step down task from 20 cm using a 5o rearfoot medial wedge (R), a 5o rearfoot and forefoot medial wedge (R/F), and a control flat insole (C). Results: Significant improvements in control were seen in the R and R/F insoles over the C insole in the foot and at the ankle and hip kinematics. The R and R/F insoles increased the knee adduction moments, but reduced knee internal rotation moment compared to the C insole. Abductor hallucis (AH) activity was reduced with both insoles, whereas tibialis anterior (TA) activity was reduced with the R insole only. Significance: Foot orthoses can change joint mechanics in the foot and lower limbs providing greater stability and less work done by AH and TA muscles. This data supports the use of foot orthoses to provide functional benefits during step descent, which may benefit patients with PFP.