The cheap over-the-counter painkiller is simply ineffective for the millions who suffer from the crippling condition, scientists have found. And they say patients might be suffering needlessly because of its perceived benefits.
Taken on its own, the drug, which costs as little as 19p a pack, does not work for osteoarthritis, however large the dose.
The research, published today, has potentially huge ramifications for the way a host of debilitating conditions are managed.
The NHS spends £85million a year handing out paracetamol, with the average prescription costing 20 times more than a supermarket packet.
Swiss researchers found diclofenac, a non-steroidal anti-inflammatory drug or NSAID, offers the most effective short-term relief.
But they warned it should not be used long-term because of side-effects.
Dr Sven Trelle, of the University of Bern, said: “NSAIDs are usually only used to treat short-term episodes of pain in osteoarthritis, because the side-effects are thought to outweigh the benefits when used longer term.
“Because of this, paracetamol is often prescribed to manage long-term pain instead of NSAIDs.
“However, our results suggest paracetamol at any dose is not effective in managing pain in osteoarthritis.”
The condition usually develops with age as cartilage – the body’s natural shock absorber – wears in hip, knee and wrist joints.
Nearly nine million people in the UK suffer from debilitating pain and stiffness, relying on daily doses of painkillers.
Many who take anti-inflammatories suffer unpleasant side-effects such as confusion, constipation and stomach bleeds.
Dr Maureen Baker, chairman of the Royal College of GPs, said: “The majority of evidence still suggests paracetamol is a safe drug for most patients, but a number of recent studies – this included – do cast doubt on its effectiveness at treating osteoarthritis.
“We know alternatives such as NSAIDs can be effective but they can have nasty side-effects for patients if they are taken over a long period.”
The Swiss team’s findings come after the largest analysis of randomised trials on osteoarthritis ever undertaken.
Experts reviewed data from nearly 59,000 patients in 74 trials between 1980 and 2015, comparing the effect of 22 different treatments.
Analysis published in The Lancet showed all 22 medications, irrespective of dose, improved symptoms of pain compared with a placebo.
Although some doses of paracetamol had a small effect improving physical function and reducing pain, it was only slightly better than the placebo and did not reach the minimum standard of clinical effectiveness.
In comparison, diclofenac at the maximum daily dose of 150mg was most effective, and better than more common anti-inflammatories including ibuprofen.
Professor Nicholas Moore, of the University of Bordeaux, said: “The most remarkable result is that paracetamol does not seem to confer any demonstrable effect or benefit in osteoarthritis, at any dose.
“This finding is not entirely unexpected. Paracetamol has been on the market for as long as most of us remember.
“Its efficacy has never been properly established or quantified in chronic diseases, and is probably not as great as many would believe.
“Many patients could be suffering needlessly because of perceived NSAIDs risks and paracetamol benefits, which might not be real.”
Richard Francis, of Arthritis Research UK, said: “While NSAIDs such as diclofenac are an effective short-term treatment, they are not recommended for long-term use due to their side-effects.
“In line with Nice guidelines, we recommend people with arthritis only use oral NSAIDs when they’re experiencing severe pain as a result of joint inflammation.”
Judi Rhys, chief executive at Arthritis Care, said: “Osteoarthritis is a condition often overlooked and its impact underestimated so we welcome research that better informs doctors how to manage the condition.”