Subject-specific toe-in or toe-out gait modifications reduce the larger knee adduction moment peak more than a non-personalized approach

Abstract

The knee adduction moment (KAM) is a surrogate measure for medial compartment knee loading and is related to the progression of knee osteoarthritis. Toe-in and toe-out gait modifications typically reduce the first and second KAM peaks, respectively. We investigated whether assigning a subject-specific foot progression angle (FPA) modification reduces the peak KAM by more than assigning the same modification to everyone. To explore the effects of motor learning on muscle coordination and kinetics, we also evaluated the peak knee flexion moment and quadriceps-hamstring co-contraction during normal walking, when subjects first learned their subject-specific FPA, and following 20 min of training. Using vibrotactile feedback, we trained 20 healthy adults to toe-in and toe-out by 5° and 10° relative to their natural FPA, then identified the subject-specific FPA as the angle where each subject maximally reduced their larger KAM peak. When walking at their subject-specific FPA, 18 subjects significantly reduced their larger KAM peak; 8 by toeing-in and 10 by toeing-out. On average, subjects reduced their larger KAM peak by 18.6 ± 16.2% when walking at their subject-specific FPA, which was more than the reductions achieved when all subjects toed-in by 10° (10.0 ± 17.1%, p = .013) or toed-out by 10° (11.0 ± 18.3%, p = .002). Quadriceps-hamstring co-contraction and the peak knee flexion moment increased when subjects first learned their subject-specific FPA, but only co-contraction returned to baseline levels following training. These findings demonstrate that subject-specific gait modifications reduce the peak KAM more than uniformly assigned modifications and have the potential to slow the progression of medial compartment knee osteoarthritis.

Keywords: Co-contraction; Gait retraining; Knee adduction moment; Knee osteoarthritis; Real-time biofeedback.

Conflict of interest statement

Conflict of Interest

We, the authors, do not have a conflict of interest related to this work.

Published by Elsevier Ltd.

Figures

Fig. 1

The reduction in the peak knee adduction moment (KAM) for each subject from a select two of the four foot progression angle (FPA) modifications; the two FPAs shown for each subject represent the FPA that yielded the greatest and least reduction in that subject’s peak KAM. Significant (p

Fig. 2

The percent reduction in the peak knee adduction moment and peak estimated medial contact force for 5° and 10° toe-in (TI) and toe-out (TO) gaits as well as at the subject-specific foot progression angle (SS FPA). When walking at their subject-specific foot progression angle, subjects achieved a greater reduction in both the knee adduction moment and medial contact force compared to when all subjects walked at any of the 5° or 10° foot progression angles. (* p

Fig. 3

(a) Vastus lateralis and (b) biceps femoris normalized muscle activity and (c) co-contraction during four phases of the gait cycle. Muscle activity and co-contraction increased from baseline to the subject-specific FPA evaluation trial. Following 20 min of training, co-contraction and biceps femoris activity reduced to baseline levels, while vastus lateralis activity remained elevated. (* p

Fig. 4

(a) The knee adduction moment (KAM) moment arm, (b) mediolateral (ML) distance between knee joint centers, and (c) mediolateral distance between centers-of-pressure during the baseline (solid), 10° toe-in (dotted), and 10° toe-out (dashed) trials. Toe-in and toe-out gaits are compared to baseline (* p