If your knee hurts and you have been managing it for a while, somebody has probably mentioned an injection.
There are three in common use, they work in completely different ways, and the evidence behind them differs considerably. Most people are offered one without ever being told how it compares to the others.
Here is an honest sort.
A boundary first. We are a physical therapy clinic. We do not give injections and we do not prescribe. These are decisions for your physician, and this article is background so that conversation is better informed.
Corticosteroid Injections
The most commonly offered, and the one most people have heard of.
What it does: delivers a potent anti inflammatory directly into the joint, with the aim of reducing pain and swelling.
What the evidence shows: a systematic review of international guidelines concluded that there is some evidence intra articular steroids are efficacious, but that the benefit may be relatively short lived, with the review specifying under four weeks.
Read that carefully. Not ineffective. Short lived.
The review also noted that care should be taken with repeated injections because of potential harm.
And guidelines disagree. Some international bodies conditionally recommend corticosteroid injection for knee osteoarthritis. Others, including Australian general practice guidelines cited in that review, have asserted that corticosteroid injections are not recommended for knee or hip osteoarthritis.
Which tells you something useful. When guideline bodies reviewing the same evidence reach different conclusions, the effect is probably real but modest, and reasonable clinicians can disagree about whether it is worth it.
How to think about it sensibly: as a window rather than a solution. If a few weeks of meaningfully reduced pain lets you do strengthening work you could not manage before, that is a good use of an injection. Taken as a standalone treatment, it buys time without changing anything.
Hyaluronic Acid Injections
Also called viscosupplementation.
What it does: hyaluronic acid is a component of normal joint fluid, and the idea is to supplement it, improving lubrication and cushioning.
What the evidence shows: the same guideline review reported good outcomes for both pain reduction and functional improvement, but with an important qualification. Most of the positive outcomes were limited to studies using high molecular weight preparations, delivered as a course of two to four injections a year.
Which means the product and the protocol matter, and results from one preparation do not necessarily transfer to another.
The broader context worth knowing: this is one of the more contested interventions in the field. Some guidelines support it, others recommend against it, and the disagreement is substantial.
Questions worth asking your physician: which preparation, how many injections, and what the expected duration of benefit is.
Platelet Rich Plasma
The newest of the three and the most heavily marketed.
What it does: blood is taken, spun to concentrate the platelets, and injected into the joint, on the basis that growth factors in the platelets promote healing.
What the evidence shows: the guideline review was direct about this. Different national society guidelines do not recommend intra articular PRP injection in the management of knee osteoarthritis, for lack of evidence.
That is a notably clearer position than for the other two, and it is worth knowing before paying for it, because PRP is typically the most expensive of the three and frequently not covered by insurance.
To be fair to it: research is ongoing, preparation protocols vary enormously between providers, and the lack of a recommendation reflects insufficient evidence rather than proof of ineffectiveness. But “we do not yet know” is a different proposition from “this works,” and you should know which one you are buying.
The Question Nobody Asks
Here is the question that changes how you evaluate any of these.
Compared to what would happen anyway over the next few months, what does this change, and for how long?
Knee osteoarthritis symptoms fluctuate naturally. People typically seek an injection when things are at their worst, which is also the point at which things are most likely to improve regardless. That makes personal experience an unreliable guide and placebo effects in this area substantial.
Which is not an argument against injections. It is an argument for having realistic expectations and a defined review point rather than an open ended arrangement.
What Should Be Happening Alongside
All three of these are symptom management. None of them build anything.
Exercise is recognized internationally as a core treatment for knee osteoarthritis. Not an adjunct, not advice. The treatment.
Strength work builds the muscle that absorbs load before it reaches the joint surfaces. Quadriceps strength in particular is both a risk factor and a treatment target.
Weight management where relevant, which directly reduces load through the knee.
And load management, adjusting demand while capacity is rebuilt.
So the honest framing of an injection is this. If it gives you a window of reduced pain, the question is what you do with the window. Spend it building strength and you come out of the period in a different position. Wait to see whether the effect holds and you come out roughly where you started, then conclude the injection did not work.
Questions Worth Taking to Your Appointment
Which injection are you recommending, and why that one for me?
What proportion of people get meaningful benefit, and for how long?
How many can I have, and over what period?
What are the risks, including with repeated injections?
What should I be doing in the weeks afterwards?
And is there anything I should try first?
A physician who engages with all six is giving you what you need to decide.
When Knee Pain Needs Assessment Before Anything Else
Seek same day medical care for a knee that is hot, red and acutely swollen, particularly with fever. Joint infection is uncommon and serious, and it is one reason injections are not given into an inflamed joint without assessment.
Seek prompt assessment for a knee that locks or will not fully straighten, a knee that gives way repeatedly, significant swelling that came on within hours of an injury, inability to bear weight, or severe unrelenting night pain.
And raise with your physician any knee pain with unexplained weight loss, fever or a history of cancer.
Make the Window Count
Whatever you decide about injections, the strength and function side is what determines where your knee is in a year.
Shiraj Physio offers a free discovery visit at no cost and no obligation. You will get a thorough assessment of your knee, strength and movement, an honest explanation of what is driving your symptoms, and a plan that makes the most of any relief you get from medical treatment.
We work alongside your physician, not instead of them.