The impact of stochastic resonance electrical stimulation and knee sleeve on impulsive loading and muscle co-contraction during gait in knee osteoarthritis.

BACKGROUND Increased impulsive loading and muscle co-contraction during gait have been observed in individuals with knee osteoarthritis. Proprioceptive deficits in this population may contribute to these effects. Proprioception has been shown to improve with the combination of stochastic resonance electrical stimulation and a knee sleeve in knee osteoarthritis. Our goal was to determine whether stochastic resonance stimulation combined with a knee sleeve would decrease impulsive loading rates and muscle co-contraction during gait in knee osteoarthritis. METHODS Gait kinetics, kinematics and muscle activity were assessed during walking in subjects with knee osteoarthritis during three different conditions: no stochastic resonance/no sleeve (control), stochastic resonance at 75% threshold/sleeve, and no stochastic resonance/sleeve. Loading rates were calculated from the ground reaction force. Muscle co-contraction was calculated from the ratio of vastus lateralis to lateral hamstring activity. Differences between conditions were assessed using a repeated measures analysis of variance (P<0.05). FINDINGS The 75% threshold/sleeve and sleeve only conditions resulted in increased knee flexion at contact and reduced loading rates compared to the control condition (P<0.05). However, these measures did not significantly differ between the 75% threshold/sleeve and sleeve only conditions. Muscle co-contraction was found to decrease with the 75% threshold/sleeve condition compared to the other conditions. INTERPRETATION Increased knee flexion and decreased loading rates may be a result of proprioceptive improvements resulting from the sleeve or sleeve/stimulation combination. The stochastic resonance stimulation did not demonstrate an ability to enhance the effects of the sleeve with the exception of reductions in muscle co-contraction.