Pre-exercise and acute movement-evoked pain trajectories during a 24-week outdoor walking program for knee osteoarthritis (WALK)

Objectives: Exploring (1) pre-exercise and acute movement-evoked pain (AMEP) during an outdoor walking program in individuals with knee osteoarthritis (OA); and (2) comparing baseline physical performance and AMEP flares initiated by walking between participants with either a higher or lower attendance rate. Methods: Individuals with knee OA were prescribed a 24-week walking program, including one unsupervised walk and two supervised walk classes per week. Participants self-reported knee pain on a numerical rating scale (NRS; 0-10) before and after each supervised class. Mixed-effects models were used to investigate trajectories over time for pre-exercise pain and AMEP change (post-minus pre-exercise pain; positive value indicates flare-up). Baseline physical performance (6 tests) and AMEP flares were compared between participants with higher (attending >_70% of supervised classes) and lower attendance rates. Results: Of 24 participants commencing the program, 7 (29%) withdrew. Over 24 weeks, pre-exercise pain improved by 1.20 NRS (95% CI-1.41 to-0.99), with estimated largest per class improvements during the first 8 weeks (-0.05 (-0.06 to-0.03) and plateauing around 20-weeks. The AMEP was estimated to improve by 0.19 NRS (95% CI-0.38 to-0.004) over 24-weeks, with improvements plateauing around 12-weeks. Participants with lower attendance (n = 11) scored poorer on all physical performance tests and experienced a slight increase in AMEP during the first two weeks of the program. Conclusions: Participants improved in pre-exercise pain and AMEP in the first 20 and 12 weeks, respectively. Despite supervision, physical performance and AMEP flares may have contributed to lower attendance. Trial registration number: 12618001097235.