Knee Osteoarthritis? Call in the Leeches!

Summarized by Robert W. Griffith, MD
December 4, 2003

Introduction

"Home is he brought, and laid in his sumptuous bed,
Where many skillful leaches him abide,
To salve his hurts, that yet still freshly bled."
Edmund Spenser, The Faerie Queene, published in 1596

In earlier time, leeches were widely used in medicine, as the above quotation reminds us. Their use has declined as modern medicines and surgical techniques have evolved, but they are still used today to relieve venous congestion and severe swelling in plastic and reconstructive surgery. Their beneficial actions are thought to be due to chemicals secreted in their saliva that can prevent clumping of platelets and interrupt blood coagulation.

For the first time in recent years, doctors have tried applying leeches to see if they can relieve pain, using osteoarthritic knees as their model. Their findings are reported in the Annals of Internal Medicine, and are summarized here.

What was done

A German teaching hospital recruited patients with osteoarthritis of the knee using newspaper advertisements. Participants had to be over 40, and have well-defined osteoarthritis with no evidence of rheumatoid arthritis, and they should not have had arthroscopy, injections into the knee joint, or knee surgery within the previous 3 months. They had to have a pain rating of more than 40 on the well-accepted Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

Fifty-one patients were randomly assigned to receive a single leech treatment, or 28 days of daily application of a non-steroidal anti-inflammatory drug, diclofenac, in a gel form. The patients returned for assessment on days 3, 7, 28, and 91 after the first treatment.

In those assigned to leech therapy, 4 to 6 medicinal leeches were applied to the knee at the most painful places. The leeches were left in place until they detached themselves, on average after 70 minutes. The control group applied diclofenac gel at least twice daily for 28 days.

The change in WOMAC pain scores was used to evaluate the success of treatment. In addition, patients completed a comprehensive questionnaire that included personal data, general medical information, clinical status, and possible side effects.

What was found

The two patient groups (leeches: 24, diclofenac: 27) were similar. The average age was 64, and there were 33 women and 18 men. Their average Body Mass Index (BMI) was 27, indicating overweight.

The WOMAC pain scores, recorded at each visit, which were around 50 at baseline, are shown in this chart:

It can be seen that leeches had a fairly immediate effect in reducing pain, measured at days 3 and 7. By day 28 the difference between leeches and diclofenac gel were no longer statistically significant - i.e. they might have occurred by chance alone.

In addition to a reduction in pain, joint function improved and stiffness decreased; these benefits persisted for 3 months. However, there were no differences between leech-treated patients and those given diclofenac gel with respect to the amount of 'rescue' medication i.e. aspirin or other pain killers.

Only minor side effects occurred in each treatment group. Mild to moderate itching, however, was reported at the leech bite spots; this lasted for 4 days, on average. Not surprisingly, the hemoglobin levels in the patients treated with leeches dropped from an average of 8.9 mmol/L before, to 8.5 mmol/L 24 hours after, application of the leeches.

What does this mean?

The investigators concluded that leech therapy seems to be an effective treatment for painful osteoarthritic knees. An accompanying editorial in the same journal is more skeptical.¹ First, the trial was not 'blinded', so that the patients and the doctors knew which form of treatment was being used, and could therefore have been influenced in their reports of pain, joint function, etc. Second, the study was very short, considering the very chronic nature of osteoarthritis, which continues for years. Experts looking at possible new drug treatments recommend a study lasting 12 weeks at least, and ideally 24 weeks.

Leeches are not usually used for treating pain, and it's hard to explain how they may work in this situation. The saliva of leeches contains factors that inhibit platelet clumping and other mechanisms of blood clotting. The investigators in this study suggest the leeches may also excrete an anti-inflammatory substance (an inhibitor of kallikrein) in their saliva, which is responsible for the pain relief.

Clearly more clinical trials are needed before leeches appear on all pharmacy shelves, next to ibuprofen and diclofenac. The real importance of this study may be the possibility of isolating and identifying a new type of anti-inflammatory agent that could lead to an innovative drug for osteoarthritis sufferers.

Source

• Effectiveness of leech therapy in osteoarthritis of the knee. A. Michalsen, S. Klotz, R. Luedtke,  et al., Ann Intern Med, 2003, vol. 139, pp. 724--730

Footnotes
1. Multidisciplinary integrative approach to treating knee pain in patients with osteoarthritis. MC. Hochberg, Editorial. Ann Int Med, 2003, vol. 139, pp. 781--783

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