Association of mechanical temporal summation of pain with muscle co-contraction during walking in people with knee osteoarthritis.

BACKGROUND:People with knee osteoarthritis walk with excessive muscle co-contraction that can accelerate disease progression. Central pain sensitization is common in people with knee osteoarthritis and may be related to walking patterns. The objective of this study was to examine the relation of central pain sensitization with muscle co-contraction during walking in people with knee osteoarthritis. METHODS:This study reports secondary analysis from baseline data of two clinical trials (n = 90 participants with knee osteoarthritis). The presence of central pain sensitization was measured by mechanical temporal summation at the patella and the wrist. Quadriceps and hamstrings activation was assessed using surface electromyography during walking at self-selected and fast paces. Muscle co-contraction indices for vastus medialis-medial hamstrings and vastus lateralis-lateral hamstrings muscle pairs were calculated during stance phases. Co-contraction outcomes were compared between people with and without mechanical temporal summation at each site, adjusting for age, sex, and body mass index. FINDINGS:People with mechanical temporal summation at the knee had greater vastus lateralis-lateral hamstrings co-contraction while walking at a fast pace (P = 0.04). None of the other differences was statistically significant, but the overall trends and effect sizes indicated greater co-contraction in people with temporal summation at the knee irrespective of gait phase, walking speed, or muscle pairs. INTERPRETATION:Central pain sensitization, assessed as mechanical temporal summation at the knee, is related to greater knee muscle co-contraction during fast walking in people with knee osteoarthritis. Thus, mitigating central sensitization may be an interventional target to reduce muscle co-contraction for people with knee osteoarthritis.