BackgroundKnee osteoarthritis (KOA) is a significant health issue because it causes pain and functional limitation. Many studies have reported that moxibustion, a treatment in traditional Korean medicine, is effective in treating KOA. However, conventional moxibustion produces smoke, harmful gases, and odors that can adversely affect the eyes, skin, and throat. It is also difficult to control the intensity of stimulation in conventional moxibustion. An electrical moxibustion device was developed to circumvent these problems, but there are few studies of that device. We will evaluate the efficacy and safety of electrical moxibustion as a treatment for KOA, and compare it with traditional indirect moxibustion and usual care.MethodsThis is a multicenter, randomized, open, assessor-blinded, parallel-group clinical trial. A total of 138 eligible participants with KOA will be randomly allocated into three groups (electrical moxibustion, traditional indirect moxibustion, or usual care) with a 1:1:1 ratio. Participants in each moxibustion group will receive 12 sessions of moxibustion treatment at 6 acupoints (ST36, ST35, ST34, SP9, EX-LE4, SP10) plus up to 2 points of “ashi”, if needed, over a period of 6 weeks (2 sessions per week). A specifically designed device that provides thermal stimulation using electrical energy will be used for the electrical moxibustion group. Participants in the usual care group will receive usual treatment and self-care. The primary outcome measure is change in pain on a numerical rating scale (NRS) from week 1 to week 6. The secondary outcome measures are pain assessed on a visual analog scale (VAS), the Korean version of the Western Ontario and McMaster osteoarthritis index (K-WOMAC), patient global assessment (PGA), and the European quality of life five dimension five level scale (EQ-5D-5 L). Safety will be assessed by monitoring adverse events at each visit. Follow-up measurements will be performed at 12 weeks after baseline measurements.DiscussionThis trial will provide evidence on the efficacy and safety of electrical moxibustion as a treatment for KOA.Trial registrationClinicalTrials.gov, NCT03287570. Registered on 19 September 2017.Electronic supplementary materialThe online version of this article (10.1186/s13063-018-2514-x) contains supplementary material, which is available to authorized users.