Though it might sound like an oxymoron, leech therapy may well succeed where other treatments fail in providing relief for the pain and inflammation of osteoarthritis, according to a new study. The findings appear in the current issue of the Annals of the Rheumatic Diseases.

In fact, leeches once were commonly used for pain relief, but fell out of favor last century. To assess the efficacy of the old-fashioned approach, Andreas Michalsen of the Essen-Mite Clinic in Essen, Germany, and colleagues conducted a pilot study involving 16 patients who had had knee pain for more than six months. X-rays revealed telltale signs of osteoarthritis in all of the participants, whose average age was 68. In addition to the exercise, physiotherapy, relaxation therapy and dietary changes the subjects had already incorporated into their treatment regimen, ten patients received leech therapy for the pain. This involved placing four medicinal leeches on the inflamed knee and leaving them there for 80 minutes. The other six patients were given conventional pain treatment.

The researchers recorded pain levels three days prior to starting pain treatment and 28 days after treatment had finished. Although the initial leech bite proved slightly painful to some of the patients, the therapy brought significant pain relief within 24 hours. The alleviation continued four weeks later, without side effects or infections. Those participants who received conventional treatment, in contrast, did not report pain relief.

As to why these reviled creatures might have such soothing effects, the authors note that leech saliva contains various analgesic, anaesthetic and histamine-like compounds. Despite the small size of their study, the researchers say, their results indicate that leech therapy deserves further study