Background: Non-pharmacological interventions for chronic knee pain are increasingly requested by patients and are recommended in current treatment guidelines. An intervention that has been used for many years for pain relief is nettle sting.

Objectives: To explore the feasibility of a definitive RCT of nettle sting for chronic knee pain, in particular the acceptability of the research to GPs and patients, and the optimal methods for recruitment and outcome measurement.

Methods: Patient blinded pilot RCT, set in two inner city primary care practices in Plymouth, UK. Potential participants were identified from practice computerised databases using three different approaches: age and analgesic use, age and appropriate Read code, or age alone. Patients had to be aged between 55 and 80 years with knee pain and a presumptive clinical diagnosis of OA knee, with a baseline WOMAC pain subscale score of more than 4. They were randomised to receive either treatment with Urtica dioica, or placebo intervention with Urtica galeopsifolia daily for 1 week. The main outcome measure for the treatment effect was the WOMAC pain subscale; other outcomes included quantitative and qualitative data to inform the design of a future study.

Results: Out of 45 patients who were eligible, 42 were recruited. Invitations targeted at patients who were both currently receiving repeat prescriptions for non-steroidal or analgesic drugs and had relevant Read codes proved most efficient for recruitment. Mean baseline WOMAC pain subscale scores were 9.2 (S.D. 3.4) and 7.9 (2.3) in the two groups. The mean reduction in pain score at the end of treatment in the nettles group was 1.7 (95% confidence interval 0.6, 2.9) and in the controls 1.6 (CI 0.5, 2.7). All GP practices, and all patients approached, were willing to be involved in the research. Patients liked the treatment mostly because it was 'natural'. The sting was acceptable and viewed as a minor irritation.

Conclusion: Research into nettle sting is acceptable to patients and GPs, and patients do not find the treatment more than a minor irritation. Larger rigorous studies are justified to determine the effectiveness of this ancient therapy.