The study focused on 16 patients, average age 68, who had had persistent knee pain for more than six months. None had sustained knee injuries and all had x-ray evidence of osteoarthritis. Exercises, physiotherapy, relaxation techniques, and dietary changes were already part of their treatment programme.
Leech therapy was tried on 10 patients, eight of whom were women. Six others were given conventional treatment for pain. Four leeches were applied to the painful knee and left in place for one hour and 20 minutes. Pain measures were recorded three days before the start of the treatment and 28 days afterwards it had finished.
Leech treatment produced rapid pain relief after three days, with the greatest effects registered 24 hours after treatment. The effects were sustained four weeks later. There were no side effects or infections, although patients described the initial leech bite as slightly painful. Pain relief was not evident in those treated conventionally.
The authors comment that leech therapy always used to be used to relieve pain and inflammation, but fell out of favour last century. They add that there are plausible explanations for the effectiveness of leech therapy, because leech saliva contains various analgesic, anaesthetic, and histamine-like compounds. The authors admit that the study is small, but suggest that the results warrant further exploration on larger numbers of patients.
[Effect of leeches therapy (Hirudo medicinalis) in painful osteoarthritis of the knee 2001;60:986]