Researchers who reviewed more than 150 studies focusing on treating knee osteoarthritis with viscosupplementation have not endorsed its ‘broad use’. Their findings raise ethical issues about the continued use of the intervention in some countries.

The international research team – led by Tiago V Pereira, from the applied health research centre at the Li Ka Shing Knowledge Institute at St Michael’s Hospital in Toronto – published its findings in The BMJ today (7 July).

Dr Pereira and his colleagues found evidence that giving injections of hyaluronic acid (known as viscosupplementation) to treat knee osteoarthritis made almost no difference to pain and might raise the risk of adverse events.

Questions over its efficacy

Though viscosupplementation has been used to treat knee osteoarthritis since the 1970s, its effectiveness and safety has often been questioned. The team reviewed studies in which viscosupplementation was used to treat patients with knee osteoarthritis that had been conducted over the past 50 years.

National and international guidelines vary in their recommendations, but most advise against the use of viscosupplementation. While National Institute for Health and Care Excellence guidelines do not recommend its use in England, healthcare systems in other countries, including the USA, continue to offer it to patients.

The researchers identified 169 trials involving 21,163 patients with knee osteoarthritis that compared viscosupplementation with placebo treatment or no treatment.

The main analysis of this review, which included a subset of 24 large trials of higher methodological quality involving 8,997 randomised patients, found that viscosupplementation was associated with a small reduction in pain compared with placebo. However, the difference was small enough to be deemed ‘clinically irrelevant’.

There is strong, conclusive evidence that among patients with knee osteoarthritis, viscosupplementation, compared with placebo, is associated with a clinically irrelevant reduction in pain intensity and with an increased risk of serious adverse events [Tiago V Pereira et al.]

Ethical concerns

The team found there had been no conclusive evidence that viscosupplementation and placebo treatment had led to the same clinical result in terms of pain reduction since 2009 – meaning there is no point in giving the injections.

Dr Pereira and his colleagues also found from 15 large trials on 6,462 randomised participants that viscosupplementation was linked to a 49 per cent higher risk of serious adverse events than placebo.

Based on their analysis of the studies published from 2009-2021 alone, they suggest that more than 12,000 patients were arguably unnecessarily subjected to these injections in viscosupplementation trials – a finding that could raise ethical concerns.

Limitations and strengths

As the study represented summary estimates it did not necessarily exclude the possibility that selected patient populations could benefit from viscosupplementation. Also, the researchers looked at adverse events that emerged rather than at adverse events that were directly and clearly related to treatment.

On the plus side was the fact that this was the largest collection of randomised trials on viscosupplementation reported to date, which significantly decreases the risk of bias influencing the results.

Conclusion

The authors conclude: ‘There is strong, conclusive evidence that among patients with knee osteoarthritis, viscosupplementation, compared with placebo, is associated with a clinically irrelevant reduction in pain intensity and with an increased risk of serious adverse events.’

They add: ‘The findings do not support broad use of viscosupplementation for the treatment of knee osteoarthritis.’

Factfile

Knee osteoarthritis is a chronic disease that involves inflammation and structural changes of the joints, resulting in joint pain and limitations to physical movement.

It is a leading cause of disability among older people, with an estimated 560 million people living with the condition globally.

To read the full version of the paper, titled Viscosupplementation for knee osteoarthritis: systematic review and meta-analysis, visit: https://www.bmj.com/content/378/bmj-2022-069722