Ankle Joint and Rearfoot Biomechanics During Toe-In and Toe-Out Walking in People With Medial Compartment Knee Osteoarthritis

Background: Toe-in and toe-out walking are 2 strategies that have been shown to be effective in reducing the knee adduction moment in people with knee osteoarthritis. However, despite a positive biomechanical impact on the knee, altering foot rotation may impart unintended forces or joint positions on the ankle that could impact joint health. The kinematic and kinetic changes at the ankle during toe-in or toe-out walking have yet to be examined. Objective: To examine ankle/rearfoot biomechanics during toe-in and toe-out walking in those with knee osteoarthritis. Design: Single-session repeated measures design to compare ankle biomechanics during walking with 4 different foot rotations. Setting: University motion analysis laboratory. Participants: A convenience sample (N = 15) of males and females with a diagnosis of medial knee osteoarthritis confirmed by radiographs. Methods: Participants walked in 4 conditions guided by real-time biofeedback: (1) toe-in (+10 degrees), (2) zero rotation (0 degrees), (3) toe-out (-10 degrees), and (4) toe-out (-20 degrees). Ankle and rearfoot kinematics and kinetics were examined during barefoot over-ground walking. Main Outcome Measures: Ankle joint angles, moments, moment impulses, and foot rotation. Results: Overall, toe-in compared to toe-out walking decreased (P = .03) peak rearfoot eversion (toe-in = -1.6 degrees; 10 degrees toe-out = -3.7 degrees; 20 degrees toe-out = -4.1 degrees). Toe-in compared to toe-out walking also increased rearfoot inversion at initial contact (7.4 degrees vs 3.1 degrees at 10 degrees toe-out and 1.9 degrees at 20 degrees toe-out; P < .001) and frontal plane rearfoot angle excursion (9.0 degrees vs 6.8 degrees at 10 degrees toe-out and 6.0 degrees at 20 degrees toe-out; P < .006). Toe-in compared to all other conditions increased peak external ankle inversion moments (0.04 Nm/kg vs 0.02 Nm/kg at 0 degrees, 0.02 Nm/kg at 10 degrees toe-out, and 0.01 Nm/kg at 20 degrees toe-out; P < .003). Conclusions: Toe-in and toe-out walking require different ankle/rearfoot biomechanics, though no differences in discomfort were observed. Longer-term studies are required to properly assess these relationships in knee osteoarthritis populations.