Arthrosamid knee injections: what the evidence shows, how it compares with PRP, and what it costs
Reviewed by The Wellness Team. Last reviewed October 2026.
Short answer: Arthrosamid is a polyacrylamide hydrogel injected into the knee to cushion the joint lining, and it has real trial evidence behind it: a 2024 randomised trial of 239 adults found a single injection was at least as effective as hyaluronic acid for knee osteoarthritis pain over one year. It is a permanent implant rather than a regenerative treatment, it is only for knees, and side effects such as short-term pain and swelling were more common with it than with hyaluronic acid in that trial, though all were mild or moderate. Whether it suits you depends on your knee, your goals and how you feel about a permanent gel versus a biological treatment like PRP.
What Arthrosamid is
Arthrosamid is a clear gel made of 2.5% cross-linked polyacrylamide and 97.5% water. A single 6 mL injection goes into the knee joint, where the gel integrates into the synovial tissue lining the joint capsule. It is non-biodegradable, meaning it is designed to stay in the joint permanently rather than being absorbed. That permanence is the selling point and the main thing to think about, in equal measure.
What the evidence shows
The strongest study is a 2024 randomised, double-blind, multicentre trial from Denmark comparing one Arthrosamid injection with one hyaluronic acid injection (Synvisc-One) in 239 adults with knee osteoarthritis. At 26 weeks, Arthrosamid was non-inferior to hyaluronic acid on pain scores, with no significant differences on stiffness, function or quality of life measures. The authors concluded it was as effective and safe as hyaluronic acid for at least a year after a single injection.
Two honest caveats. First, adverse device effects were reported by 28.9% of the Arthrosamid group versus 7.6% of the hyaluronic acid group, all mild or moderate, but a real difference. Second, most of the longer-term data, including a 12-month open-label study and a published three-year follow-up, comes from research groups connected to the product. Independent replication is still thin.
Arthrosamid versus PRP: an honest comparison
These are different philosophies. Arthrosamid is a synthetic cushion: a permanent gel that stays in the joint. PRP is a biological stimulus: platelets concentrated from your own blood, injected to influence the joint environment, and gone within days while their signalling effects play out.
We apply the same honesty to our own treatment. The 2021 RESTORE trial in JAMA, with 288 adults, found PRP was no better than saline for knee osteoarthritis at 12 months, so anyone promising you certain results from knee PRP is overstating the evidence, including if it is us. Some people report meaningful improvement, the trial averages are sobering, and NICE guidance does not currently recommend PRP for osteoarthritis. If your knee is the problem, the conversation starts with what the evidence can and cannot promise, not with a price list.
Who each option may suit
- Arthrosamid may suit someone with confirmed knee osteoarthritis who wants a single-injection option and is comfortable with a permanent synthetic implant.
- PRP may suit someone who prefers an autologous treatment with nothing foreign left behind, accepts the evidence is mixed, and wants the option of repeating treatment.
- Neither replaces the basics: strengthening, weight management where relevant, and proper diagnosis first. If you have not had a recent assessment or imaging, that is the starting point.
What it costs with us
We do not offer Arthrosamid; our regenerative joint treatment is PRP. Joint PRP is £750 per session, ultrasound guided, with an assessment first so we only treat people the evidence could plausibly help. If Arthrosamid sounds like the better fit for you after reading this, we would rather tell you that than sell you the wrong thing.
Want a straight answer on your knee? Message us on WhatsApp and we will talk through what the evidence says for your situation.
Frequently asked questions
Is Arthrosamid permanent? Yes, by design. The gel is non-biodegradable and stays in the joint lining. For many people that durability is attractive, but it also means the decision is harder to reverse than a course of PRP.
How long does Arthrosamid last? The 2024 randomised trial followed people for a year and found benefit maintained, and a three-year follow-up has been published. Longer independent data is still limited.
Is Arthrosamid better than PRP? They have never been compared head-to-head in a trial. Arthrosamid has non-inferiority evidence against hyaluronic acid; PRP has mixed trial results, including one large trial where it matched saline. A proper assessment matters more than the brand of injection.
Do you offer Arthrosamid? No. We offer ultrasound-guided PRP at £750 per session, and we will tell you honestly if we think your knee points elsewhere.
Still deciding? Message us on WhatsApp and we will help you think it through.