Metformin relieves knee osteoarthritis pain: Study

New research from Monash University has found metformin can provide pain relief for patients living with knee osteoarthritis and overweight or obesity.
 
With long-established efficacy in type 2 diabetes, the study, published this month in JAMA, concluded that metformin can also reduce pain for people with knee arthritis.
 
Through a randomised clinical trial, researchers compared the use of daily metformin in those with symptomatic knee osteoarthritis and coexistent overweight or obesity with a placebo. 
 
With 107 participants, 73 women and 34 men with a mean age of 58.8, the study found those taking metformin reported a 31.3-point reduction in pain after six months, compared to 18.9 for the placebo group. Knee pain was measured on a 0–100 scale, with 100 being the worst.
 
The results come at a time when no new osteoarthritis drugs have been approved in Australia since celecoxib (sold as Celebrex) and rofecoxib (sold as Vioxx) in the late 1990s.
 
Lead researcher Professor Flavia Cicuttini said metformin ‘fills the gap’, providing GPs with an alternative they could offer patients in addition to lifestyle measures.
 
‘Metformin improves knee pain in people with symptomatic knee osteoarthritis who are overweight and obese, the effect is present at six months, and it has a moderate effect size, bigger than non-steroidal anti-inflammatory drugs,’ she told newsGP.
 
‘The biggest concern is the idea that there are no treatments, so most of the recommendations keep pushing weight loss and exercise, which makes a lot of sense, but most patients who go to a GP will say “I’ve already tried that and it doesn’t work”.
 
‘This has the potential of just adding something else, where the GP and the patient can work together.’
 
Professor Cicuttini said that in the last 10 years, she has seen an increase in knee replacements for early osteoarthritis.
 
She described this trend as worrying as ‘we know dissatisfaction rates with technically great knee replacements are between 20 and 30%’.
 
‘Knee replacements for earlier osteoarthritis are 2.5 times more likely to have patients unhappy than if people have them for later osteoarthritis,’ she said.
 
‘The other issue is that if you have a knee replacement earlier in life, you’re likely to need revision surgery.’
 
The Monash University study found metformin did not work immediately for osteoarthritis patients, with data showing pain relief at six months, but not at three months – but the reason for this is still being explored.
 
Ultimately, Professor Cicuttini described metformin as a ‘different way’ to treat pain.
 
‘GPs are very familiar with metformin, which is a low-cost, safe medication,’ she said.
 
‘It could be provided to patients in addition to other treatments they use and has the potential to delay people having knee replacements before they are absolutely needed.
 
‘If people on metformin have less knee pain and are able to do more physical activity, then knee replacements can wait.’

The study’s researchers now hope to conduct a larger clinical trial to confirm their results, as well as working with consumers and healthcare professionals, including GPs and orthopaedic surgeons, to introduce metformin into the knee osteoarthritis management pathway.
 
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