Defrin 2005.

Methods	Randomised controlled trial 6‐arm parallel group design Trial duration: 4 weeks No power calculation reported
Participants	62 patients randomised 62 patients with knee OA reported at baseline Study joints: 62 knees Average age: 67 years
Interventions	Experimental intervention: noxious adjusted interferential current stimulation in group 1, noxious unadjusted interferential current stimulation in group 2, innocuous adjusted interferential current stimulation in group 3, innocuous unadjusted interferential current stimulation in group 4, 3 times per week Control intervention: sham interferential current stimulation, 3 times per week Duration of treatment period: 4 weeks Analgesics allowed, unclear whether intake was similar between groups. Device: Uniphy: Phyaction electrical stimulator Self‐administered: no Waveform: interferential Pulse width: not applicable Pulse frequency: 30 to 60 Hz (beat) Amplitude: above sensory threshold, 2 groups 30% above pain threshold; 2 groups 30% below pain threshold Duration of stimulation per session: 20 minutes Electrodes: 2 of 8 x 6 cm wet sponge electrodes Placement: medial and lateral aspects of the knee, 2 cm from outer margins of patella
Outcomes	Extracted pain outcome: global pain after 4 weeks, described as "chronic pain intensity (VAS)" No function outcome reported No primary outcome reported
Notes	1 out of 6 trial arms, the no‐intervention control group was excluded in the review
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?	Unclear risk	Use of sham device: Uniphy‐Phyaction electrical stimulator, however the device described as shut‐off
Incomplete outcome reporting: intention‐to‐treat analysis performed? Pain	Unclear risk	No information provided
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