Previous trials have shown that acupuncture can relieve pain, but many have been small and it is difficult to decide whether the benefits identified are simply the result of the placebo effect.

The German study, published in Arthritis & Rheumatism, compared the experience of 357 patients given immediate acupuncture with a further 355 whose treatment started three months later.

Benefits were measured on the WOMAC scale, a widely used scale of disease severity which measures pain, stiffness, and how well the joint works. At the start of treatment the patients' scores on the scale were about 50.

After 15 sessions in the first three months, the patients treated with acupuncture had WOMAC scores of about 30, while the control group still waiting for treatment remained about 50.

After adjusting for other factors, the improvement in the score was 36 per cent. After six months the control group, which began its treatment three months later, showed the same level of improvement. In all cases normal care continued alongside the acupuncture treatments.