Wang 2009

Methods	Randomised controlled trial.
Participants	Inclusion criteria: aged > 55 years, body mass index ≤40 kg/m2, WOMAC pain subscale score (VAS version) >40 (range 0‐500), and fulfilment of the ACR criteria for knee OA with radiographic Kellgren/Lawrence scale knee OA grade ≥ 2. Exclusion criteria: none specified. Country: US. Sample number: IG: 20; CG: 20. Mean age: 72 years. Progress Plus: gender: mixed; high school education: 100%.
Interventions	Provider(s): qualified Tai Chi Master/instructor. Training: yes. Setting: hospital. Content: warm up and review of Tai Chi principles and techniques; Tai Chi exercises; breathing techniques and relaxation methods. Length/intensity: twice weekly for 12 weeks. Control: attention placebo/alternative intervention; wellness education and stretching programme.
Outcomes	At 48 weeks: pain (WOMAC); function (WOMAC); self‐efficacy (Self‐Efficacy score).
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random assignment by statistician using computer‐generated numbers to randomise permuted blocks of sizes 2 and 4.
Allocation concealment (selection bias)	Low risk	Sealed, opaque envelopes.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and providers unblended to treatment allocation.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Blinded outcomes assessment.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition: IG 0% (0/20); CG 0% (0/20). ITT analysis.
Selective reporting (reporting bias)	Low risk	All outcomes reported.
Other bias	Low risk	No other bias detected.