A common diabetes drug has been linked to a reduction in the need for joint replacement surgery. The observational study suggests the drug could be helpful for patients with osteoarthritis, although further clinical work is needed to validate the association.

Over the last few years a few small studies have speculated on the potential for metformin to slow the pace of joint deterioration associated with osteoarthritis. Animal studies have offered mechanistic clues to how this drug may help treat osteoarthritis, but large observational work in humans has been lacking.

This new research fills the gap by studying the health records of around 40,000 people with type 2 diabetes. Half of the cohort were treated with metformin, while the other half served as controls.

Over a 14-year follow-up period the researchers found those patients taking metformin were 30% less likely to need either a hip or a knee replacement compared to the group not taking metformin. Of those joint replacement procedures, around 90% were due to osteoarthritis.

One of the big questions coming out of this study is exactly how metformin could be affecting osteoarthritis degeneration. Diabetes and osteoarthritis have often been linked, with diabetes being a clinically recognized risk factor for osteoarthritis.

Some studies have speculated insulin resistance may play a role in the development of osteoarthritis. So it’s plausible to speculate effectively treating diabetes could reduce the risk of osteoarthritis. But the more compelling implication is that metformin can more directly influence osteoarthritis in the absence of any diabetic symptoms.

“The biological mechanisms linking metformin and osteoarthritis are yet to be clarified,” the researchers write in the study. “Metformin could decrease the risk of total joint replacement among patients with diabetes mellitus by multiple mechanisms, including by reducing inflammation, by sustaining adenosine 5′-monophosphate–activated protein kinase activity in chondrocytes and by regulating metabolism.”

There is currently no direct pharmacological treatment for osteoarthritis. The condition can only be managed through exercise, weight loss and pain relieving drugs. Affecting around 15% of people over the age of 60, it’s estimated that by 2030 around half a million people will require either total hip replacement or total knee replacement surgery. So there is certainly a need for some kind of treatment that can slow the progression of this degenerative disorder.

The researchers do stress the limitations of their study, suggesting there may be limits to how generalizable these findings are for osteoarthritis patients who are not suffering from type 2 diabetes. However, they do note the therapeutic effect of metformin on osteoarthritis is plausible and clinical trials specifically focusing on the association are warranted.

The new study was published in the Canadian Medical Association Journal.