Knee osteoarthritis is a common and disabling condition. Previous reviews of Tai Chi for knee osteoarthritis have focused on physical health outcomes. This systematic review aimed to estimate the effects of Tai Chi compared to non-exercise intervention (eg, education), usual care or physiotherapy on both physical and mental health in people with knee osteoarthritis.
Searches were performed in eight databases (including PubMed, Embase and PEDro). Randomised controlled trials that involved participants with knee osteoarthritis and compared Tai Chi to non-exercise intervention (eg, education), usual care or physiotherapy were included. Key outcomes were physical and mental health. Two reviewers independently selected trials for inclusion, extracted data, and evaluated trial quality and certainty of evidence. Disagreements were resolved by discussion or arbitration from a third reviewer. Trial quality was evaluated using the Cochrane risk of bias tool. Certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Meta-analyses were used to calculate the standardised mean between-group difference (and its 95% confidence interval (CI)) of change from baseline to follow-up for each outcome.
16 trials (986 participants) were included in the meta-analyses. The trials were conducted in the United States (n=7 trials), China (6) and Korea (3) and recruited people with knee osteoarthritis with a mean age of 60 to 79 years. About 80% of participants were women. Three styles of Tai Chi were evaluated (Yang (n=7 trials), Sun (3), Qigong (1), unclear (5)), and treatment duration ranged from 8 to 52 weeks. Tai Chi was compared to usual care in 9 trials, education in 5 trials, and physiotherapy in 2 trials. Physical health was quantified using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function subscale in 13 trials (note: lower scores indicate better function, so a negative between-group difference indicates better physical function in the Tai Chi groups). Mental health was quantified using the 36-Item Short Form Survey (SF-36) mental component summary score in 5 trials (note: higher scores indicate better mental health, so a positive between-group difference indicates better mental health in the Tai Chi groups).
Mean physical health in the Tai Chi groups was 0.9 standard deviations lower than in the control groups (95% CI 0.7 to 1.1 lower; 13 trials; 844 participants; moderate certainty). This translates to an absolute mean lowering of 8 points (95% CI 6 to 10 lower) on the 0- to 68-point WOMAC physical function subscale compared to control (note: the baseline standard deviation from the Osteoarthritis Initiative study and guidance from the Cochrane Handbook v6.1 were used to calculate this estimate).
Mean mental health in the Tai Chi groups was 0.3 standard deviations higher than in the control groups (95% CI 0.1 to 0.5 higher; 5 trials; 409 participants; moderate certainty). This translates to an absolute mean difference of 2 points (95% CI 1 to 4) on the 0- to 100-point SF-36 mental component summary score (note: the baseline standard deviation from Wang et al 2016 was used to calculate this estimate).
Tai Chi probably improves physical and mental health in people with knee osteoarthritis. The small difference in the SF-36 mental component summary score is unlikely to be clinically meaningful.
Hu L, et al. Tai Chi exercise can ameliorate physical and mental health of patients with knee osteoarthritis: systematic review and meta-analysis. Clin Rehabil 2020 Sep 21:Epub ahead of print