Researchers, who carried out what they claimed was the first proper study of its kind, found no evidence the bands have any benefits.

The devices have been used for centuries, but academics and charities are urging people not to waste money on “ineffective” gimmicks.

Stewart Richmond, who led the study at York University, said: “It appears that any perceived benefit obtained from wearing a magnetic or copper bracelet can be attributed to psychological placebo effects. People tend to buy them when they are in a lot of pain, then when the pain eases off over time they attribute this to the device.

“However, our findings suggest such devices have no real advantage over placebo wrist straps that are not magnetic and do not contain copper.”

While the bracelets in themselves are harmless, Mr Richmond added, people with osteoarthritis should be “cautious” about spending large sums of money on something that won’t help them. Magnets from disused speakers would be cheaper, he added, but equally pointless.

The trial at York’s department of health sciences, which worked jointly with researchers from the NHS and the universities of Hull and Durham, involved 45 people aged 50 or over who were all suffering from osteoarthritis.

Each participant tested four different devices – two wrist straps with different levels of magnetism, a copper bracelet and a demagnetised placebo wrist strap – over a 16-week period. The study looked at factors including pain relief, stiffness and physical function but found no significant differences between the bracelets.

Mr Richmond’s findings were welcomed by the Arthritis Research Campaign (ARC), which said the results were “certainly not a surprise”.

Jane Tadman, a spokeswoman for the charity, said: “We wouldn’t want people to spend money on products that haven’t been proven.”

An earlier ARC survey found that two-thirds of all pain-relief products on the UK market “didn’t work at all”, Ms Tadman added.

One product their testers recommended was capsaicin gel, a product made from chillies, which sufferers rub into their skin. Fish oil could also be helpful they said – particularly fish body oil, rather than the more common liver oil – while glucosamine sulphate tablets were only moderately successful.

Ms Tadman said there may be a placebo effect with copper and magnetic bracelets, which could explain why some users have found them helpful.

A vast industry in arthritis aids has sprung up in recent years, with prices starting at around £15 for a bracelet.

Proponents say the copper can be absorbed through the skin to rectify deficiencies in the body, which they say are due to localised copper surges at the affected joints.

Online magnet stores boast their products can “improve” blood flow and quality.

It is also claimed the magnetic bracelets can prevent nerves from sending pain signals to the brain.