Gel Injections for Knee Arthritis
Hyaluronic acid gel injections — Synvisc, Durolane, Monovisc and similar — are widely advertised for knee arthritis and specifically recommended against in the Australian guideline. What the evidence shows, and what to ask before paying.
Hyaluronic acid injections — sold as Synvisc, Durolane, Monovisc, Euflexxa and other brands, and often described simply as “gel injections” or “lubricating injections” — are among the most heavily marketed treatments for knee arthritis.
The Australian guideline is unambiguous about them: viscosupplementation is not recommended for knee osteoarthritis. It sits in the do-not-offer category, not the uncertain one.
That is a strong statement, so it is worth explaining where it comes from rather than simply asserting it.
The idea, and why it is appealing
Hyaluronic acid is a real component of normal joint fluid. It contributes to the fluid’s viscosity, and in an arthritic knee the fluid is measurably thinner and less effective than in a healthy one.
The reasoning follows naturally: replace what has been depleted, restore the lubrication, reduce the pain. It is one of the most intuitively satisfying explanations in orthopaedics, which is a large part of why the treatment has persisted.
What the trials found
When hyaluronic acid is compared against a placebo injection — saline into the same joint — the difference has generally been too small to matter clinically.
The more informative pattern is what happens as trial quality improves. The larger and better-controlled the trial, the smaller the measured effect. That relationship is a well-recognised signature of an effect that is not real, rather than one that is real but modest.
There is also a substantial placebo response to having any injection into a painful knee, which is considerable and well documented. Some of what people experience after gel injections is that response — which is genuine relief, but not relief attributable to the hyaluronic acid.
Why it is still widely offered
Worth addressing directly, because being told a widely available treatment is not recommended is confusing.
- It is safe. The risk of harm is low, so the case for trying it is not a case against safety.
- Some people report real benefit. Guidelines describe averages; individuals are not averages, and a person who improves after an injection is not lying.
- It is a billable procedure. This is not an accusation of bad faith — but a treatment that generates revenue faces less pressure to be discontinued than one that does not.
None of that makes offering gel injections improper. It does mean you should know the evidence position when the offer is made, especially when the money is yours.
What it costs
Generally not covered by Medicare for knee osteoarthritis in Australia, so the cost is usually out of pocket — commonly several hundred dollars for a course, sometimes considerably more depending on the product and whether it is a single injection or a series.
If you are considering it, ask for the total figure, including consultation and administration fees, before agreeing.
What to ask before paying
Three questions worth putting to whoever is offering it:
- What benefit should I expect, and for how long?
- What does the current Australian guideline say about this treatment?
- What would you suggest instead, and why is this better for my knee specifically?
A clinician comfortable answering all three is one worth listening to. Reluctance on the second question is informative.
The honest alternative
If gel injections are off the table, the question becomes what to do instead.
Exercise and weight management are the two strongly recommended treatments, and both cost less than a course of injections. A cortisone injection is a reasonable option for settling a flare, with the honest caveat that it is short-lived.
And if those have genuinely been tried — not token attempts, but a real go — and the knee is still limiting the things you care about, that is the point at which surgical options are worth a proper conversation rather than another injection.
Next: PRP and stem cell injections — or back to the overview.
Do gel injections work for knee arthritis?+
The Australian guideline does not recommend offering viscosupplementation for knee osteoarthritis, placing it in the do-not-offer category rather than the uncertain one. Trials comparing hyaluronic acid against placebo injection have generally found differences too small to be clinically meaningful, and the higher-quality trials tend to show smaller effects than the weaker ones — a pattern that usually indicates the effect is not real.
What are Synvisc, Durolane and Monovisc?+
Brand names for hyaluronic acid preparations injected into the knee, a treatment known as viscosupplementation. Hyaluronic acid is a component of normal joint fluid, and the rationale is that supplementing it restores lubrication and cushioning in an arthritic joint. The rationale is plausible; the difficulty is that the clinical trials have not borne it out.
Why are gel injections still offered if the guideline recommends against them?+
Several reasons. They are safe, so there is little harm in trying; some patients report benefit; and guidelines describe averages across populations rather than individuals. It is also relevant that they are a billable procedure. None of that makes offering them improper, but it is worth knowing the evidence position when you are being offered one, particularly when you are paying.
Are gel injections covered by Medicare in Australia?+
Generally not for knee osteoarthritis, and cost is usually out of pocket — often several hundred dollars per course, sometimes more. Costs vary by product and provider, so ask for the total figure including any consultation and administration fees before committing.
Are gel injections safe?+
Broadly yes. The commonest problems are local — pain, swelling or a reaction in the joint after injection, which usually settles. Serious complications are uncommon. The argument against them is about effectiveness rather than safety, which is a genuinely different objection: the question is not whether they will hurt you but whether you are paying for something that works.
What should I try instead of gel injections?+
The two treatments strongly recommended in the Australian guideline are land-based exercise and, where relevant, weight management. Both cost less than a course of gel injections and have substantially better evidence. A corticosteroid injection is a reasonable option for short-term relief of a flare. If those have been genuinely tried and the knee is still limiting your life, that is the point at which surgical options are worth discussing.