If you have knee osteoarthritis and you're trying to avoid — or delay — a knee replacement, two newer injections keep coming up: Arthrosamid and PRP. They're often mentioned in the same breath as "regenerative" options, but that's misleading. They work in almost opposite ways, and understanding that difference is the key to choosing well. This physician-reviewed blog post covers what each one actually does, what the evidence shows, and what type of knee pain would benefit from each.
The shared goal
Knee osteoarthritis is a whole-joint problem: thinning cartilage, low-grade inflammation, and a joint that's become mechanically and biologically unhappy. Both of these injections aim to reduce pain and improve function without surgery — but one does it by cushioning the joint and the other by stimulating repair.
How Arthrosamid works
Arthrosamid is a 2.5% polyacrylamide hydrogel — a soft, water-based gel. In a single injection, it's placed into the knee, where it integrates into the synovial lining (the inner capsule of the joint) rather than being absorbed and cleared like older "gel shot" hyaluronic acid. The result is a durable cushioning and lubricating effect, plus changes in the joint lining that appear to reduce pain. It does not try to regrow tissue; it changes the joint's mechanical and inflammatory environment.
The headline appeal is durability from a single treatment. Extension studies of polyacrylamide hydrogel for knee osteoarthritis have reported statistically significant, clinically relevant reductions in pain, stiffness and function (WOMAC subscales) maintained for years after one 6 ml injection, with a good safety profile — our Arthrosamid page summarizes the evidence out to 5 years. The evidence base is younger and smaller than hyaluronic acid's, but it is growing, and a comparative study versus hyaluronic acid has added support.
How PRP works
Platelet-rich plasma takes the opposite approach. We draw your blood, concentrate the platelets in a centrifuge, and inject that concentrate into the knee. Platelets release growth factors that recruit repair cells and calm the destructive inflammation inside the joint. PRP isn't a cushion — it's a biological signal, aimed at improving the joint environment and slowing the process rather than mechanically padding it.
PRP has the deeper evidence base of the two for knee osteoarthritis. Multiple meta-analyses of randomized trials — including a 2024 pooled analysis in PLOS One and a meta-analysis of double-blinded randomized trials — have found PRP outperforms hyaluronic acid injections for pain and function, with benefits typically lasting 6–12 months and often requiring a repeat course. Quality of preparation and injection accuracy matter, which is why our PRP is physician-performed with ultrasound guidance.
The practical comparison
Mechanism. Arthrosamid: a permanent-integrating gel that cushions the joint and calms the lining. PRP: your own concentrated platelets, delivering repair signals into the joint.
Number of injections. Arthrosamid: usually a single injection. PRP: typically 1–3 sessions per course, sometimes repeated annually.
How long it lasts. Arthrosamid: durability data out to several years (up to 5) from one treatment. PRP: commonly 6–12 months, then a repeat course.
Evidence base. PRP: larger and more mature — multiple meta-analyses of randomized trials. Arthrosamid: promising and growing, with multi-year data, but younger and from smaller studies.
Cost (our pricing). Arthrosamid: $3,900 per knee (single injection). PRP: $950–$1,400 per session. Over a few years the totals can end up closer than they first appear, since PRP is usually repeated. Full details on our price list. Neither is OHIP-covered; many extended plans reimburse physician-performed injections.
Best-suited stage. Arthrosamid: designed for knee osteoarthritis specifically, including moderate-to-more-advanced joints where cushioning and pain relief are the goal. PRP: often favoured for mild-to-moderate arthritis where there's more repair biology to work with, and it can be used in other joints and tendons too.
So which one?
Choosing usually comes down to what you're optimizing for:
- Arthrosamid tends to suit patients who want a one-and-done treatment with multi-year durability, who have moderate-to-advanced knee OA where regrowth is unrealistic and reliable pain relief is the priority, and who prefer to avoid a repeating schedule of injections.
- PRP tends to suit patients with mild-to-moderate arthritis where there's more healthy tissue to stimulate, those who want the option with the deepest randomized-trial evidence, and those treating tendons or multiple areas, not just the knee joint space.
They're not mutually exclusive over a lifetime, either — some patients use PRP earlier in the disease and consider Arthrosamid later as the joint advances. And a third path exists: prolotherapy or Prolozone®, which targets the ligaments stabilizing the knee rather than the joint surface, and can complement either. If you're comparing the biologically active options against each other, our prolotherapy vs PRP piece goes deeper.
One honest boundary for all of them: none regrows cartilage in a truly bone-on-bone knee. Arthrosamid can still provide meaningful pain relief at that stage because it works by cushioning rather than repair — but if the joint has structurally failed, a surgical conversation may be the right one, and we'll tell you that plainly.
Getting assessed in Toronto or Oakville
At Upper Room Clinic, both Arthrosamid and PRP are physician-performed, performed by Dr. Biljana Kostovic, MD and our other regenerative pain doctors with over 30 years in integrative and chronic pain medicine. A knee assessment covers your imaging, arthritis stage and goals, and ends with a specific recommendation — Arthrosamid, ultrasound-guided PRP, a regenerative approach like Prolozone®, or a surgical referral if that's genuinely the better path. Eligible chronic pain patients can also ask about our OHIP-covered interventional pain program.
Book a discovery call and we'll help you match the treatment to your knee — not the other way around.
