Cheing 2003.

Methods	Randomised controlled trial 4‐arm parallel group design Trial duration: 4 weeks Randomisation stratified according to gender No power calculation reported
Participants	40 patients randomised 38 patients with knee OA reported at baseline Study joints: 38 knees Number of females: 34 of 38 (89%) Average age: 66 years
Interventions	Experimental intervention: 20 min TENS in group 1, 40 min TENS in group 2, 60 min TENS in group 4, 5 times per week Control intervention: sham TENS, 5 times per week Duration of treatment period: 2 weeks Unclear whether analgesics were allowed and whether intake was similar between groups Device: ITO 120Z TENS (dual channel) Self‐administered: no Waveform: not reported Pulse width: 200 µsec Pulse frequency: 100 Hz Amplitude: above sensory threshold, strong but comfortable Duration of stimulation per session: 20 minutes Electrodes: 4 of 2 x 3 cm rubber electrodes Placement: 4 acupuncture points extra 31,32, ST35, GB34, SP9
Outcomes	Extracted pain outcome: pain on walking after 4 weeks, described as "pain during walking (VAS)" No function outcome reported No primary outcome reported
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	No information provided
Allocation concealment?	Unclear risk	No information provided
Free of selective reporting?	Unclear risk	Trial protocol not accessible, methods section not explicit about pre‐specified outcomes
Adequate blinding of patients?	Low risk	Sham device: electronic circuit disconnected, no current passed, but indicator light on
Incomplete outcome reporting: intention‐to‐treat analysis performed? Pain	High risk	30 out of 30 (100%) randomised to experimental and 8 out of 10 (80%) randomised to control group were analysed
Incomplete outcome reporting: intention‐to‐treat analysis performed? Function	Unclear risk	Not applicable
Funding by commercial organisation avoided?	Unclear risk	No information provided
Funding by non‐profit organisation?	Unclear risk	No information provided