Magnetic bracelets reduce pain in osteoarthritis of the hip and knee, according to a study funded by the Arthritis Research Campaign.

Researchers from the Peninsula Medical School, Universities of Exeter and Plymouth, said they could not be certain whether the resulting reduction in pain could be attributed to the specific effect of the magnets or the placebo effect, or both. The study was published in the Christmas edition of the British Medical Journal.

GP Dr Tim Harlow and colleagues recruited 194 patients aged 45-80 years with osteoarthritis of the hip or knee from five rural general practices in Devon. Patients wore either a standard strength magnetic bracelet, a weak magnetic bracelet, or a non-magnetic (dummy) bracelet for 12 weeks. Changes in pain were recorded using a recognised pain scoring scale.

They found a significant reduction in pain scores between the standard and dummy magnet groups. The results for the weak magnet group were similar to those of the dummy magnets, which suggests that the magnetic strength of the bracelet is important.

The authors emphasised that the benefits were in addition to existing treatments, which should not be suddenly stopped without discussion with their doctor. They also noted that high strength magnets (170mTesla or more) seem to be needed.

Although factors such as use of painkillers and patients' beliefs about the type of bracelet they were testing did not affect the results, the authors said they could not be certain whether their findings were due to a specific effect of magnets or a placebo effect. But, whatever the mechanism, the benefit from magnetic bracelets seemed clinically useful.

The (one-off) cost of bracelets also compared well with that of painkillers, such as paracetamol and anti-inflammatory drugs, and larger investigations should now test the safety of magnets relative to the well-known risks of these drugs, said the team.

Dr Harlow added that further work was needed to replicate the findings and determine whether the effect extended beyond 12 weeks

A spokeswoman for the Arthritis Research Campaign said: "We funded this study because we wanted to establish if there was any evidence for the claims made on behalf of magnetic bracelets; and we didn’t want the public to waste their money on devices that didn't work.

"Results appear to show that wearing a magnetic bracelet does reduce pain in people with hip and knee osteoarthritis although it is still unclear whether this effect is due in some part to the placebo effect. As magnetic bracelets are quite cheap and safe, people with osteoarthritis might want to consider wearing them as part of their self-help regime."