Influence of foot progression angle on the lower-limb joints and trunk using an ankle orthosis

Knee osteoarthritis decreases the ability to perform many daily activities such as walking. Thus, individuals adapt their initial movement strategy to compensate this deficit. One such compensatory strategy is to increase the foot progression angle. In order to study its impact on the lower limb joints and the trunk, we developed an ankle orthosis able to mechanically constrain the ankle external rotation. We compared four walking conditions: 1) normal walking; 2), 3) and 4) walking with the orthosis with a mechanical constraint of 0°, 10° and 20° respectively. The orthosis increased the ankle external rotation by 6° during the swing phase compared to normal walking in the 20° condition. This change led to a decrease in ankle extension, trunk sway and hip flexion on the equipped side. We therefore observed mechanical adaptations at multiple joints of the lower limb and at the trunk in response to the orthosis constraint.