Smith 1983.

Methods	Randomised sham controlled trial 2‐arm parallel group design Trial duration: 8 weeks Randomisation stratified according to gender Multicentre trial with 2 centres No power calculation reported
Participants	32 patients randomised 30 patients with knee OA reported at baseline Study joints: 30 knees Number of females: 20 of 30 (67%) Average age: 68 years
Interventions	Experimental intervention: TENS, twice per week* Control intervention: sham TENS, twice per week* Duration of treatment period: 4 weeks Analgesics intake assessed and found to be similar between groups Device: RDG Tiger Pulse Self‐administered: no Waveform: square Pulse width: 80 µsec Pulse frequency: 32 to 50 Hz Amplitude: above sensory threshold, adjusted up to a comfortable tingling sensation Duration of stimulation per session: 20 minutes Electrodes: 4 Lec Tec pads applied with electrode jelly Placement: tender knee points or acupuncture points (SP9, xiyan and UB40)
Outcomes	Extracted pain outcome: global pain after 8 weeks, described as "Weekly pain score derived from daily pain recording (linear 7‐point scale)"** No function outcome reported No primary outcome reported
Notes	*Preceded by 1 'standard' week without any treatment, **No pain outcome data presented, investigators were contacted, but we did not receive any reply. This study only contributed in safety analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk	Computer generated. Quote: "(...) assigned by random computer programme and effected by using sealed envelopes containing cards which defined the treatment (...)".
Allocation concealment?	Unclear risk	Sealed assignment envelopes, but unclear whether these were opaque and sequential
Free of selective reporting?	High risk	No results reported for some outcomes mentioned in the methods section, including sleep disturbance
Adequate blinding of patients?	Low risk	Use of sham device: RDG Tiger Pulse with broken electrode connection at jack point, no current passed but flashing light on. Quote: "Exactly the same procedure were followed for both the treatment and control groups".
Incomplete outcome reporting: intention‐to‐treat analysis performed? Pain	High risk	15 out of 16 (0.94) randomised to experimental and 15 out of 16 (0.94) 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