Short answer. Probably not. In the largest and best run trials, gel injections eased knee pain no more than a placebo injection, and they carried a small extra risk of serious side effects.

Evidence grade. Probably does not help.

What it is

Hyaluronic acid is a gel like substance found naturally in joint fluid. Injection products made from it are often called gel injections or viscosupplements. The idea is to add cushioning and lubrication to a worn knee. A course is usually between one and five injections, depending on the product.

What the research shows

The largest review pooled 89 trials with about 12,700 adults with knee arthritis. Taken together, the injections reduced pain by a moderate amount compared with a placebo injection or no injection. But the result depended on how well the trial was run. Small trials, and trials where the people measuring pain knew who had the real injection, showed large benefits. The 18 largest trials, where those measuring the result did not know, found a benefit too small to matter to patients. Five trials that were never published found no benefit at all.¹

The same review found a higher risk of serious side effects in people given the injections. Serious problems were uncommon in both groups, but there was no sign of a benefit to set against them.¹

Guidelines have followed the evidence. The American Academy of Orthopaedic Surgeons does not recommend the injections for routine use, and the UK National Institute for Health and Care Excellence says not to offer them.^2,3 Most other major guidelines have also moved away from recommending them.

Risks and effort

Most people have a sore knee for a day or two after an injection. Infection is rare. The main drawback is a delay in starting treatments that do help.

What usually works instead

Exercise and strength work for the leg muscles, weight loss where that applies, and simple pain relief have the best evidence for knee arthritis. A cortisone injection can ease a flare for a few weeks. When pain still limits daily life, knee replacement is the treatment with the most reliable results. See Osteoarthritis of the Knee and Does exercise work for knee arthritis?.

Questions people ask

A friend had a year of relief from gel injections. Is that possible?

Yes, some people feel better for months after an injection, and that is real for them. The question is how many of those people would have felt the same after a placebo injection. In the large blinded trials the answer was almost all of them.

Is one brand better than another?

Products differ in how they are made and how many injections make a course. Trials have not shown that any brand beats a placebo once the trial is large and well run.

Are gel injections safer than cortisone?

They avoid some of the problems of cortisone, such as a short rise in blood sugar. But the review above found more serious side effects with the gel than with placebo, and cortisone has at least been shown to give short term relief.

Can gel injections delay a knee replacement?

There is no good evidence that they do. The trials measure pain over weeks to months, not how long a knee lasts before it needs replacing.

References

Rutjes AWS, Jüni P, da Costa BR, Trelle S, Nüesch E, Reichenbach S. Viscosupplementation for osteoarthritis of the knee: a systematic review and meta-analysis. Ann Intern Med. 2012;157(3):180-191. https://doi.org/10.7326/0003-4819-157-3-201208070-00473
American Academy of Orthopaedic Surgeons. Management of osteoarthritis of the knee (non-arthroplasty): evidence-based clinical practice guideline. 3rd ed. Rosemont (IL): AAOS; 2021.
National Institute for Health and Care Excellence. Osteoarthritis in over 16s: diagnosis and management. NICE guideline NG226. London: NICE; 2022.

Last reviewed 22 October 2026. Next review due October 2028.