Altering foot progression angle in people with medial knee osteoarthritis: the effects of varying toe-in and toe-out angles are mediated by pain and malalignment

Objectives: To evaluate if altering the foot progression angle (FPA) by varying magnitudes during gait alters the external knee adduction moment (RAM), knee flexion moment (KFM), knee extension moment (REM) and/or symptoms in people with medial knee osteoarthritis (OA). Potential influence of pain and knee malalignment on load-modifying effects of FPA was investigated. Design: Participants (n = 22) underwent 3-dimensional gait analysis to measure KAM peaks, RAM impulse, KFM and REM peaks. Following natural gait, five altered FPA conditions were performed in random order (10 degrees toe-in, 0 degrees FPA, 10 degrees toe-out, 20 degrees toe-out and 30 degrees toe-out). A projection screen displayed their real-time FPA. Pain/discomfort at knees and feet/ankles were evaluated for each condition. Linear mixed models were used for statistical analysis. Results: Toe-in reduced the early stance peak RAM and REM but increased the RAM impulse, late stance peak and RPM. Toe-out reduced the RAM impulse, late stance peak and KFM (P < 0.001) but increased the early stance peak RAM and REM. All effects were greater in participants with more varus knees. Pain significantly mediated the effect of altered FPA on the RAM impulse and late stance peak. In more painful individuals, toe-in was predicted to reduce the RAM impulse and late stance peak, and increase them for toe-out gait. There were no immediate symptomatic changes. Conclusions: Effects of altered FPA vary across all medial knee load parameters and it is difficult to determine an optimal direction of FPA change. Future studies should consider Western Ontario McMaster Universities OA Index (WOMAC) pain to judge the likely effects of altered FPA. Crown Copyright (C) 2013 Published by Elsevier Ltd on behalf of Osteoarthritis Research Society International. All rights reserved.