Online Unsupervised Tai Chi Intervention for Knee Pain and Function in People With Knee Osteoarthritis

Importance: Tai chi is a type of exercise recommended for knee osteoarthritis, but access to in-person tai chi can be limited. Objective: To evaluate the effects of an unsupervised multimodal online tai chi intervention on knee pain and function for people with knee osteoarthritis. Design, Setting, and Participants: The RETREAT study was a 2-group superiority randomized clinical trial enrolling participants who met clinical criteria for knee osteoarthritis in Australian communities from August 2023 and November 2024. Interventions: Participants in the control group received access to a purpose-built website containing information about osteoarthritis and exercise benefits. Participants in the intervention group received the My Joint Tai Chi intervention comprising access to the same website plus tai chi information, a 12-week unsupervised video-based Yang-style tai chi program, and encouragement to use an app to facilitate program adherence. Main Outcomes and Measures: Changes in knee pain during walking (Numeric Rating Scale; range 0-10 with higher scores indicating greater pain) and difficulty with physical function (Western Ontario and McMaster Universities Osteoarthritis Index; range 0-68 with higher scores indicating greater dysfunction) during 12 weeks. Secondary outcomes included another knee pain measure, sport and recreation function, quality of life, physical and mental well-being, fear of movement, self-efficacy, balance confidence, positive activated affect, sleep quality, global improvement, and oral medication use. Results: Of 2106 patients screened, 178 met inclusion criteria and were randomized, 89 (mean [SD] age, 61.0 [8.7] years; 66 female [74%] and 23 [26%] male participants) to the control group and 89 (mean [SD] age, 62.1 [7.3] years; 59 [66%] female and 30 male [34%] participants) to the tai chi intervention. Of the total, 170 (96%) completed both of the primary outcomes at 12 weeks. The tai chi group reported greater improvements in knee pain (control, -1.3; tai chi, -2.7; mean difference, -1.4 [95% CI, -2.1 to -0.7] units; P < .001) and function (control, -6.9; tai chi, -12.0; mean difference, -5.6 [95% CI, -9.0 to -2.3] units; P < .001) compared to the control group. More participants in the tai chi than in the control group achieved a minimal clinically important difference in pain (73% vs 47%; risk difference, 0.3; 95% CI, 0.1 to 0.4; P < .001) and function (72% vs 52%; risk difference, 0.2; 95% CI, 0.1 to 0.3; P = .007). Between-group differences for most secondary outcomes favored tai chi, including another knee pain measure, sport and recreation function, quality of life, physical and mental well-being, global improvement, pain self-efficacy, and balance confidence. No associated serious adverse events were reported. Conclusions and Relevance: This randomized clinical trial found that this unsupervised multimodal online tai chi intervention improved knee pain and function compared with the control at 12 weeks. This free-to-access web-based intervention offers an effective, safe, accessible, and scalable option for guideline-recommended osteoarthritis exercise. Trial Registration: ANZCTR Identifier: ACTRN12623000780651.