Biological, biomechanical, and pain sensitivity effects of walk-run in people with self-reported knee osteoarthritis

Objectives: Participating in small volumes of high-impact exercises, such as running, is beneficial to mitigate age-related musculoskeletal deterioration. The biological and pain effects of small volumes of running integrated within a walking program in people with knee osteoarthritis (OA) are unclear. This study aims to investigate the biological and pain responses to a walk-run program in people with self-reported knee OA. Methods: Eight participants with self-reported knee OA completed a 25-minute walk-run program on a force-plate instrumented treadmill with optical motion capture. Peak knee moment and cumulative knee moment impulse were quantified during this exercise task. Pressure pain threshold (PPT) was measured at the knee and elbow before and immediately after the task. A cartilage stress marker, cartilage oligomeric matrix protein (COMP), was measured at baseline, immediately after exercise (Post), and 30 min after exercise (Post30). Results: PPT did not significantly change at the knee (Δ=7.28%, P = 0.700) or elbow (Δ=-9.15%, P = 0.496). Percentage COMP significantly increased from baseline immediately post-exercise (Hedges' g = 1.43), then returned to baseline concentration at Post30 (Hedges' g = 0.07). No significant correlations were observed between COMP and knee joint moment indices. Conclusions: Including short periods of running within a primarily walking-based session does not lead to prolonged elevations in cartilage stress markers or altered pain sensitivity. Future research with larger sample sizes and with longer follow-up, should explore whether walk-run approaches provide a practical way for people with knee OA to engage in higher-impact exercise.