Knee Osteoarthritis Treatment & Ultrasound-Guided Injection

Knee osteoarthritis is one of the most common causes of ongoing knee pain. It's often described as "wear and tear", but that's an oversimplification. Osteoarthritis affects the whole joint, the cartilage, bone, joint lining (synovium), menisci and the surrounding muscles. Just as importantly, how much change shows up on an X-ray doesn't reliably predict how much pain you feel. So my job is to look at your symptoms, your function, your activity levels and your goals, not just the scan, and build a plan around what will genuinely help you move better.

What is knee osteoarthritis?

Osteoarthritis (OA) is a whole-joint condition. Over time the cartilage thins, the underlying bone remodels, the joint lining can become inflamed (synovitis), and the muscles that support and control the knee often weaken. This is why two people with similar X-rays can have very different levels of pain and disability.

The practical message is simple: the severity on imaging doesn't always match the severity of your symptoms. Treatment should be guided by how the knee affects your daily life, your activity and your objectives, rather than by the X-ray alone.

Exercise: the foundation of treatment

Exercise is one of the best-supported treatments for knee osteoarthritis. A 2024 Cochrane review confirmed that therapeutic exercise improves pain and physical function compared with no exercise (Lawford et al., 2024). A good programme usually combines lower-limb strengthening, aerobic activity and a progressive return to the daily or sporting activities that matter to you.

More exercise isn't automatically better. Very heavy resistance training hasn't been shown to beat lower-intensity strengthening for knee OA. What really counts is progression, consistency and finding a programme you can keep up.

Exercise also isn't just "the thing you try before an injection". In a major randomised trial, people who had physical therapy had better pain and function at one year than those who had a corticosteroid injection (Deyle et al., 2020). Rehabilitation is a treatment in its own right.

Evidence: good

Weight management can make a real difference

If you're carrying extra weight, reducing it can substantially lower the mechanical load through the knee, and may also influence the low-grade metabolic inflammation linked with OA.

This became especially relevant after the STEP 9 trial in the New England Journal of Medicine: in people with obesity and symptomatic knee OA, weekly semaglutide combined with lifestyle changes produced substantially greater weight loss and significantly greater improvement in knee pain than placebo (Bliddal et al., 2024). This doesn't prove that weight-loss medication regrows cartilage, but for the right patient, effective weight management should increasingly be seen as part of treating the arthritis, not as a separate issue.

Evidence: good, weight loss improves symptoms

Injections for knee osteoarthritis

There's no single "best injection" for every arthritic knee. Different injections work in different ways, last for different lengths of time and carry different levels of supporting evidence. I'll be straight with you about each, and an injection should be there to help you move, exercise and stay active, not as an isolated fix.

Corticosteroid

Corticosteroid injections are mainly anti-inflammatory. They're most useful when the knee is acutely painful, swollen or has an effusion or synovitis, because they can settle pain quickly and let you get back to walking and rehab. The main limitation is that the benefit is generally short-term.

Repeated, routine steroid injections are harder to justify. A landmark JAMA trial in which triamcinolone was injected every three months for two years found greater cartilage loss than with saline, and no better long-term pain relief (McAlindon et al., 2017). That doesn't mean an occasional steroid injection causes meaningful damage, but it argues against using repeated scheduled steroids as a long-term strategy.

My view: corticosteroid is most useful for an inflammatory flare, or for short-term pain relief to get rehab moving, rather than as a repeated long-term treatment.

Evidence: good for short-term relief, not for repeated long-term use

Hyaluronic acid

Hyaluronic acid (HA), sometimes called viscosupplementation, has been used for knee OA for decades (see my full guide to hyaluronic acid injections). The evidence is genuinely mixed: a large 2022 BMJ meta-analysis concluded that the average improvement over placebo is relatively small, and NICE doesn't recommend its routine use (Pereira et al., 2022; NICE NG226, 2022).

However, HA studies are very varied. Different products have different molecular weights, cross-linking, injection schedules and patient groups, so it's hard to reduce to a simple "works" or "doesn't work". In practice, some people get meaningful relief lasting several months, others get little.

My view: HA remains a reasonable option for selected patients with mild-to-moderate OA who are still symptomatic despite rehab, particularly when steroid isn't desirable. It's a symptomatic treatment, not a proven cartilage-regenerating one, and the response varies.

Evidence: mixed / variable

Platelet-rich plasma (PRP)

PRP is prepared from your own blood and concentrates the platelets that release growth factors. Many meta-analyses report greater improvement with PRP than with steroid or HA, particularly between about 6 and 12 months, and more recent placebo-controlled analysis also suggests clinically meaningful gains in pain and function (Bensa et al., 2025). Results between individual trials have varied, though, and there's an increasingly important reason why.

Not all PRP is the same. "PRP" isn't a standardised drug. Preparations differ in platelet concentration, total platelets injected, volume, white-cell and red-cell content, technique and number of injections. Simply calling an injection "PRP" tells you little about what was actually delivered.

Platelet dose appears to matter. What counts may be the total dose delivered, that is, platelet concentration multiplied by the volume injected. A 2024 triple-blind randomised trial comparing roughly 2.8 billion with 5.6 billion platelets found both groups improved, but the higher dose produced significantly greater and more sustained improvement (Patel et al., 2024). A systematic review reached a similar conclusion: trials reporting good outcomes used substantially higher platelet doses on average than those reporting failure (Berrigan et al., 2024). It's too early to set a universal threshold, but the signal points to roughly 5 billion or more platelets per injection as a potentially important range.

PRP is also usually given as a course of two to three injections spaced a few weeks apart, rather than a single treatment.

My view: PRP can be a reasonable option for well-selected patients with mild-to-moderate knee OA who want a potentially longer-lasting biological treatment, but I don't currently offer PRP at Insight MSK. I've included it here so you have the full picture. The preparation method and the actual platelet dose matter, and PRP shouldn't be described as proven to regrow normal cartilage.

Evidence: promising, dose appears to matter

Polyacrylamide hydrogel (Arthrosamid®)

Injectable polyacrylamide hydrogel (iPAAG), marketed as Arthrosamid®, is a newer option. Unlike HA, steroid or PRP, it's a non-biodegradable hydrogel designed to integrate with the joint lining after a single injection. A multicentre randomised trial comparing one 6 mL iPAAG injection with HA found it non-inferior for symptom improvement, with benefit maintained to one year (Bliddal et al., 2024), and longer-term follow-up of the same patients has since shown improvements sustained for up to five years after a single injection (Bliddal et al., 2026).

These longer-duration results are encouraging, especially from a single injection. Arthrosamid doesn't yet have the volume of independent evidence available for HA or PRP, and I'll always discuss that openly.

My view: Arthrosamid is becoming a reasonable option for persistent knee OA when appropriate conservative care hasn't been enough and you're looking for longer-duration symptom control, particularly to postpone or avoid surgery. Read more on my dedicated Arthrosamid® page.

Evidence: promising for prolonged relief from a single injection

Steroid vs HA vs PRP vs Arthrosamid, at a glance

None of these injections has been shown to regenerate established cartilage loss. The decision to inject should rest on realistic goals, settling pain and enabling rehabilitation, rather than promises of regeneration.

Why I use ultrasound guidance

Knee injections can be done using surface landmarks alone or under real-time ultrasound guidance. Ultrasound lets me see the joint, the needle and the surrounding structures as I work, identify an effusion, synovial thickening or a Baker's cyst, and drain fluid when it's appropriate.

The benefit goes beyond accuracy. A 2024 systematic review and meta-analysis of four randomised trials (338 patients) found that, compared with landmark-guided injection, ultrasound guidance meant less procedural pain, better pain outcomes and better function, with patient satisfaction also favouring ultrasound (Oo et al., 2024). An experienced clinician can certainly inject a knee by landmarks, but when you've chosen an injectable, especially an expensive one such as PRP, HA or Arthrosamid, it makes sense to confirm the treatment is actually delivered inside the joint.

My view: I perform knee injections under ultrasound guidance whenever appropriate, to maximise accuracy, assess the joint at the same time and make sure the medication reaches its target.

Evidence: good, ultrasound improves accuracy and outcomes

When should you consider knee replacement?

Total knee replacement remains a highly effective treatment for the right patient with advanced, symptomatic OA. It's normally considered when pain and loss of function substantially affect your quality of life despite appropriate non-operative treatment. As with everything in OA, the decision should be based on your symptoms and function, not the X-ray appearance alone.

My approach to knee osteoarthritis

Treating knee OA isn't just about choosing an injection. Before anything else, I work through three questions:

1. What's driving your symptoms? Structural OA, synovitis, an effusion, mechanical loading, muscle weakness and metabolic factors all contribute differently between people.
2. What can we change? Exercise, strength, activity and weight management remain fundamental.
3. Is an injection appropriate? If symptoms are still limiting, we choose according to your OA severity, inflammatory activity, age, previous response and goals.

Broadly, the injections I offer are corticosteroid for rapid, short-term control of a flare, hyaluronic acid for variable but potentially useful medium-term relief, and Arthrosamid for prolonged relief from a single injection. PRP is a promising medium-to-longer-term option in mild-to-moderate OA, where an adequate platelet dose seems to matter and treatment usually means a course of injections, but it isn't something I currently provide. Surgery is considered when severe symptoms persist despite reasonable non-operative care. Ideally, an injection helps you move better, exercise, strengthen the leg and stay active, rather than standing alone.

Frequently asked questions

References