Neuromuscular alterations exist with knee osteoarthritis presence and severity despite walking velocity similarities.

BACKGROUND: Neuromuscular strategies during walking in individuals with knee osteoarthritis are being explored for diagnostic information; however, isolating differences to disease progression is difficult given walking velocity decreases with osteoarthritis severity. This study investigated lower extremity electromyograms during walking in asymptomatic individuals and individuals with different severities of knee osteoarthritis who walked with similar self-selected velocities.
METHODS: Muscle activity in lateral and medial gastrocnemius, vastus lateralis and medialis, rectus femoris and the lateral and medial hamstrings was monitored during self-selected walking in 230 subjects with asymptomatic knees, moderate and severe knee osteoarthritis. Sixteen asymptomatic individuals, 16 individuals with moderate and 15 individuals with severe knee osteoarthritis were identified based on similarities in average walking velocity. Principal component analysis was employed to derive amplitude and temporal characteristics of the electromyographic (EMG) waveforms. Analysis of variance models tested for group and muscle differences in principal pattern scores (α=0.05). Bonferroni post hoc testing was utilized on all significant findings.
FINDINGS: Despite similar walking velocities, individuals with moderate knee OA had elevated and prolonged quadriceps and elevated lateral hamstring activity compared to asymptomatic individuals (P<0.05). A diminished phase shift between medial and lateral gastrocnemius muscle activation, greater and prolonged lateral compared to medial hamstring activation were found in the severe group compared to asymptomatic and moderate knee OA groups (P<0.05).
INTERPRETATION: Lower extremity neuromuscular function during walking is altered with the presence and severity of knee osteoarthritis and not simply a direct function of walking velocity.