Yurtkuran 1999.

Methods	Randomised controlled trial 4‐arm parallel group design Trial duration: 2 weeks No power calculation reported
Participants	100 patients randomised, 25 per group 100 patients with knee OA reported at baseline Study joints: 100 knees Number of females: 91 of 100 (91%) Average age: 58 years
Interventions	Experimental intervention: TENS, 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: MEA‐TENS (dual channel) Self‐administered: no Waveform: rectangular Pulse width: 1000 µsec Pulse frequency: 4 Hz* Amplitude: above sensory threshold, up to muscle contraction, just below pain tolerance threshold Duration of stimulation per session: 20 minutes Electrodes: 4 small MEA rubber electrodes Placement: 4 acupuncture points SP‐9, GB‐34, ST‐34, ST‐35
Outcomes	Extracted pain outcome: global pain after 2 weeks described as "Overall present pain intensity at rest (Likert)" Extracted function outcome: walking disability after 2 weeks, described as "50 foot walking time (in minutes)" No primary outcome reported
Notes	Two out of 4 groups, the electroacupuncture and ice massage groups, were excluded in this review. *Investigators named their intervention AL‐TENS, but we coded it low frequency TENS in our analysis.
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: MEA‐TENS with broken lead at jack plug, no current passed but red indicator light on. Quote: "(...) treatment appeared to be done in the same way as the other groups without the subjects suspecting the nature of the stimulation".
Incomplete outcome reporting: intention‐to‐treat analysis performed? Pain	High risk	Investigators reported that "no subject was withdrawn either active or placebo groups". However, the reported degrees of freedom indicate that 5 out of 100 patients were not included. It remained unclear to which of the 4 groups the excluded patients belonged.
Incomplete outcome reporting: intention‐to‐treat analysis performed? Function	High risk	See above
Funding by commercial organisation avoided?	Unclear risk	No information provided
Funding by non‐profit organisation?	Unclear risk	No information provided