Objective: Muscle co-activation has been shown to be elevated in individuals with knee osteoarthritis (OA) during gait. Comparisons of muscle co-activation across different activities of daily living such as stair negotiation have yet to be explored. The aim of this study was to explore muscle co-activation across different activities of daily living in patients with knee OA. Methods: Muscle co-activation was assessed in 77 symptomatic knee OA patients (mean ± SD age 62.5 ± 8.1 years, body mass index 29.4 ± 6.0 kg/m 2 , and sex 48:29 female:male) using electromyography (EMG), during a series of walking, stair negotiation (ascent, descent), and sit-to-walk activities. EMG was recorded from 7 sites, mediolateral gastrocnemius, biceps femoris, semitendinosus, vastus lateralis/medialis, and rectus femoris, and normalized to maximal voluntary isometric contraction. Correlation was used to assess the consistency of co-activation across activities. Repeated-measures analysis of variance assessed the muscle combination by activity differences. Results: Muscle co-activation was highest during stair ascent. When comparing muscle combinations within the same activity, we found that correlations ranged from r = 0.003 to r = 0.897, of which 80% of the combinations were significant. Between activities, muscle co-activation was significantly different (P <0.05). Mediolateral muscle co-activation was higher than hamstrings/quadriceps across activities. Conclusion: Two muscle co-activation strategies were observed during activities of daily living in patients with knee OA to maintain stability. Muscle co-activation was higher during more challenging activities, particularly when the joint was accepting load. Mediolateral muscle co-activation was higher than hamstrings/quadriceps, so that mediolateral co-activation was thought to be a stabilization mechanism, while hamstrings/quadriceps co-activation responds to knee flexion moments, suggesting that different muscle combinations may have different roles in responding to joint demand.
- muscle co-activation
- knee osteoarthritis
- daily living
Smith, S. L., Allan, R., Marreiros, S. P., Woodburn, J., & Steultjens, M. P. M. (2019). Muscle co‐activation across activities of daily living in individuals with knee osteoarthritis. Arthritis Care & Research, 71(5), 651-660. https://doi.org/10.1002/acr.23688