The neuromuscular demands of altering foot progression angle during gait in asymptomatic individuals and those with knee osteoarthritis

SummaryObjectivesTo determine the immediate effects of a toe-out foot progression angle modification during gait on the major lower limb muscle activation characteristics and to establish whether asymptomatic individuals and those with moderate knee OA have similar responses.DesignSeventeen patients with knee OA and 20 asymptomatic control subjects participated. Informed consent was obtained. Electromyographic (EMG) recordings were acquired from the lateral and medial gastrocnemii, vastus lateralis, vastus medialis, rectus femoris and the lateral and medial hamstrings during neutral and toe-out walking conditions. The EMG waveforms were amplitude normalized to maximal voluntary isometric contractions and time normalized to the gait cycle. Principal component analysis extracted principal waveform features. Analysis of variance models tested for main effects and interactions. Bonferroni post hoc testing was employed (α=0.05).ResultsBoth groups altered foot progression angle by approximately 15° during toe-out walking (P<0.05). A shift in gastrocnemius activation towards later stance (P<0.05) and increased magnitude and duration of quadriceps activation (P<0.05) was found. A differential activation occurred in the overall magnitude and principal shape of the lateral and medial hamstring musculature in the asymptomatic group only (P<0.05). Significant group differences were shown in each muscle analysis (P