Ahn 2017

Methods	Parallel RCT
Participants	Country of study: USA Setting: laboratory Condition: OA knee Prior management details: not reported n = 41 randomised, 40 analysed Age, mean (SD): active group 60.6 (9.8) years, sham group 59.3 (8.6) years Duration of symptoms: not reported Gender distribution: 19 M, 21 F
Interventions	Stimulation type: tDCS Stimulation parameters: tDCS 2mA intensity, 20 min Stimulation location: M1 contralateral to painful side Number of treatments: x 1 daily for 5 days Control type: sham tDCS
Outcomes	Primary: pain NRS anchors 0 = no pain, 10 = worst pain imaginable When taken: 1 d postintervention, 3 weeks postintervention Secondary: WOMAC function score AEs
Notes	Funding source: supported in part by the Claude D. Pepper Older American's Independence Center (P30 AG028740), the Universityof Florida Center for Cognitive Aging and Memory, and NIA Grants K07AG04637 and K01AG050707, and R01AG054077. This Work was also partially supported by VA HSR&D Houston Center for Innovations in Quality, Effectiveness and Safety (CIN# 13‐413), Michael E. DeBakey VA Medical Center, Houston, TX. COI: study authors declared no COI
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “randomly assigned with a ratio of 1 to 1 to either the active tDCS (n ¼ 20) or sham tDCS group (n ¼ 20) using a covariate adaptive randomization procedure so that the two groups had approximately equal distribution regarding age, gender and race.”
Allocation concealment (selection bias)	Low risk	Quote “Allocation concealment was ensured as the randomization codes were released only after all the interventions and assessments were completed.”
Adequate blinding of participants?	Unclear risk	Comment: evidence that participant blinding can be inadequate at intensity of 2 mA. No assessment of blinding success. No formal assessment of blinding success
Adequate blinding of assessors?	Unclear risk	Comment: evidence that assessor blinding can be inadequate at intensity of 2 mA. No assessment of blinding success. No formal assessment of blinding success
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: only one participant withdrew.
Selective reporting (reporting bias)	Low risk	Comment: outcomes reported adequately
Study Size	High risk	Comment: n = 20
Study duration	Unclear risk	Comment: 3‐week follow‐up
Other bias	Unclear risk	Comment: statistically significant between‐group difference in pain NRS scores at baseline