Can Arthrosamid give you more time before knee replacement?
It may give you time, and that is not the same as delaying surgery. Arthrosamid can reduce knee pain and improve function enough for some people to defer knee replacement by choice. Current research has not proved that it delays surgery compared with rehabilitation, no injections or another treatment.
Less pain makes surgery feel less urgent. Proven surgical delay would mean showing that Arthrosamid changes when knee replacement happens compared with another approach, and no study has done that.
Arthrosamid is used for symptomatic knee osteoarthritis, which commonly causes activity-related pain, stiffness and reduced movement. It manages symptoms. It does not restore the knee’s earlier structure, and it does not remove the possibility of needing knee replacement later.
What it may buy you is the ability to walk further, sleep more comfortably, or return to the exercise that supports the joint. NICE (National Institute for Health and Care Excellence), which covers England, advises considering knee replacement referral when symptoms substantially affect quality of life and suitable non-surgical care has failed or is unsuitable. Your symptoms and daily capabilities should continue to guide that decision.
What Is In This Article
Five-year data supports durability
Arthrosamid may improve your pain and function, and follow-up now extends to five years, with sustained average improvement among people who stayed in the study. Patients maintain a statistically significant reduction in pain at 5 years. Average WOMAC pain scores improve by approximately 16 points—well above the standard Minimal Clinically Important Difference (MCID) of 9 points (Bliddall, 2026).
It is a non-absorbable polyacrylamide hydrogel, meaning a water-based gel that stays in the knee joint permanently.
Sustained symptoms can be meaningful
Longer-lasting relief may give you a genuine opportunity to build strength, stay active and work out whether your knee remains manageable without surgery. Pain scores matter. So does whether you can walk, work, manage stairs and get through the day.
A manufacturer’s expected device lifetime describes the product. Your response is individual, and a study average cannot predict it.
Can we predict the success of Arthrosamid?
While the injection can provide significant symptom relief that may allow a patient to voluntarily postpone an operation, this delay is a secondary behavioural outcome rather than a proven disease-modifying effect.
Gao et al. (2025) carried out an observational cohort study tracking 269 patients (representing 314 treated knees) who received a single Arthrosamid (iPAAG) injection and followed their outcomes for 24 months.
This study identified four independent factors that predicted a positive, clinically meaningful response to Arthrosamid:
- A lower Kellgren-Lawrence grade (milder X-ray changes).
- Older age.
- An absence of diabetes.
- Having bilateral rather than unilateral knee osteoarthritis.
Your knee and goals determine whether Arthrosamid suits you
Suitability is a clinical judgement rather than something you can settle for yourself. The injection is intended for adults with symptomatic knee osteoarthritis whose conservative treatment, such as exercise, physiotherapy or pain relief, has not given adequate results.
Rob Mast personally assesses your symptoms, examines the knee and uses a real-time ultrasound scan before deciding whether Arthrosamid has a clear target and is appropriate for you. One study (Gao et al., 2025) found that lower X-ray grades were associated with better odds of meaningful improvement, though imaging is only part of the picture.
Several things feed into that decision:
- Your current function. How the pain affects walking, stairs, work, sleep and whatever you are trying to keep doing.
- What you have already tried. Exercise, physiotherapy, pain relief and previous injections all show how the knee has responded so far.
- The skin around the injection site. Active skin disease or infection near the knee makes injection unsuitable until it has settled.
- What you are hoping for. Arthrosamid may offer symptom control. It cannot promise that knee replacement will never be needed.
One thing to weigh before you commit: the gel is permanent. It is not absorbed or removed afterwards, so this procedure is a decision to take as seriously as any other lasting change to the joint. Ask what it would mean for you if knee replacement became the right answer later anyway.
Sonoscope charges £2,300 for an Arthrosamid injection. The all-inclusive fee covers clinical examination, diagnostic ultrasound, the ultrasound-guided injection and a scan report. Assessment, scan and treatment can all take place in one visit if the findings support an injection, which is convenient for people travelling from St Albans, Hertford and across Hertfordshire.
When knee replacement becomes more relevant
Knee replacement becomes more relevant when your knee continues to limit your quality of life despite suitable non-surgical care. Age, body weight and an X-ray score alone do not determine whether surgery is needed.
| Option | What it can reasonably offer | When it becomes more relevant |
|---|---|---|
| Continued non-surgical care | Therapeutic exercise, weight management where appropriate, and support with daily activity | While symptoms stay manageable and you can keep doing what matters to you |
| Arthrosamid | A possible period of lower pain and better function, for selected people | Where other forms of conservative care have given limited relief and assessment identifies a clear injection target |
| Knee replacement | A surgical option for substantial ongoing pain and loss of function | Where symptoms substantially affect quality of life, or non-surgical options are unsuitable |
If Arthrosamid does not give you enough benefit, knee replacement remains available afterwards. Whether you can live your normal life with acceptable pain and function tells you if more time without surgery is actually serving you.
Common questions about Arthrosamid and knee replacement
Does Arthrosamid work for severe or grade 4 knee osteoarthritis?
In severe or end-stage (KL Grade 4) knee osteoarthritis, the benefit of Arthrosamid drops off substantially. At this stage, mechanical friction drives the pain more than synovial inflammation, as the knee exhibits “bone-on-bone” contact and extensive structural collapse.
How long does Arthrosamid take to work?
- First 24 to 48 Hours: Some patients report a slight reduction in pain, though it is also very common to feel mild swelling, stiffness, or a sensation of “fullness” in the knee as the hydrogel disperses and the joint adapts.
- 4 to 6 Weeks (Onset of Action): This is when the hydrogel completes its initial integration into the synovial fluid and lining. During this window, most patients begin to notice a clinically meaningful improvement in their day-to-day pain levels and mobility.
- 12 Weeks / 3 Months: By this point, the hydrogel is fully incorporated into the synovial membrane, acting as a permanent, elastic scaffold. Experts consider the 12-week mark to be the “true test” of the injection’s success, representing the peak level of symptom relief.
Can you still have a knee replacement after Arthrosamid?
Yes. Arthrosamid injection does not negatively impact a subsequent total knee arthroplasty (TKA). Clinical data and surgical reports confirm that the hydrogel does not complicate the procedure or compromise the final joint replacement
Is Arthrosamid better than hyaluronic acid?
When comparing Arthrosamid (2.5% iPAAG) directly with hyaluronic acid (HA), the evidence—primarily from the ROSA randomised controlled trial (Bliddall et al. 2022) and subsequent cohort studies—shows that the key differentiator is durability of effect rather than a significant difference in initial symptom reduction. At 52 weeks, the ROSA RCT found a slight numerical advantage for iPAAG, but no statistically significant difference in overall pain reduction between the two treatments. However. With Arthrosamid, pain relief and functional gains remain statistically significant at 3, 5, and even 10 years after a single 6ml injection. Hyaluronic acid injections rarely last beyond 12 months, requiring repeat injections to maintain their benefits.
What are the main risks of Arthrosamid?
Common and expected reactions (Post-Injection Flare)
- A foreign volume (6 ml of hydrogel) can trigger an initial inflammatory response when introduced into the joint space. Pain and Stiffness: Often worsening for 24–48 hours once the local anaesthetic wears off.
- Swelling and Effusion: A sensation of fullness or visible swelling is common. In most cases, the pain is mild to moderate and self-limiting.
- Duration: This flare typically settles within 1 to 2 weeks without specific intervention beyond standard analgesia and rest.
Rare but serious risks:
- Septic Arthritis: As with any intra-articular procedure, introducing bacteria into the joint space is the most severe risk. Symptoms include rapid onset of severe pain, a hot joint, extreme swelling, and systemic fever.
- The “Permanence” Factor: Because Arthrosamid is a non-biodegradable scaffold, an infected joint is significantly more complex to manage than one injected with degradable steroids or HA. Eradicating the infection may require aggressive surgical debridement or joint washout.
- Foreign Body Reactions: Though highly biocompatible, there are rare reports of chronic inflammation, nodule formation, or material migration requiring surgical removal.
- Hypersensitivity: Allergic reactions to polyacrylamide are theoretically possible, though not commonly reported in clinical trials.
This is general information, not medical advice.
Reviewed by Rob Mast, Advanced Practice Physiotherapist and Sonographer, Honorary Lecturer in Musculoskeletal Diagnostic Ultrasound at Brunel University.
References:
Bliddal, H., Beier, J., Hartkopp, A., Conaghan, P. G., & Henriksen, M. (2022). One-year performance of polyacrylamide hydrogel vs. hyaluronic acid: A randomised controlled study. Osteoarthritis and Cartilage, 30, S370-S371.
Bliddal, H., Beier, J., Hartkopp, A., Conaghan, G.C. and Henriksen, M., (2026). Sustained symptom relief and safety over five years following a single intra-articular injection of 2.5 [%] polyacrylamide hydrogel in patients with knee osteoarthritis. Clin. Exp. Rheumatol.
Gao, H.C.K., Akhtar, M., Creedon, C., Nar, Ö.O., Verma, T. and Lee, P.Y., (2025). Polyacrylamide hydrogel injections in knee osteoarthritis: A PROMs-based 24-month cohort study. Journal of Clinical Orthopaedics & Trauma, 69.
