Arthrosamid vs PRP vs HA hyaluronic acid: What’s best for knee osteoarthritis?

Arthrosamid is an injectable polyacrylamid hydrogel, (iPAAG), a synthetic, non-biodegradable, water-based polymer designed for intra-articular use in knee osteoarthritis. It is designed to function as a long-lasting joint lubricant and space filler.

For specific treatment information, please see the following links: Arthrosamid , PRP for knee arthritis. We also offer hyaluronic acid with Durolane, Monovisc, and SportVis. All of our injections are ultrasound guided.

iPAAG consists of a cross-linked polyacrylamide network with high water content typically 2.5–4% polymer, 96–97.5% water), forming a soft, viscoelastic gel. After njection, it integrates into the synovial tissue, forming a stable sub-synovial layer raversed by connective tissue and covered by synovial lining, with histological evidence of persistence for up to two years in animal models.^[1] This integration is thought to contribute to its durability and sustained symptomatic effect.

Mechanistically, iPAAG provides joint lubrication, reduces friction at the cartilage surface, and may help buffer mechanical stress. In vitro studies show that polyacrylamide hydrogel significantly lowers the friction coefficient of both healthy and degraded cartilage explants, functioning as a viscous lubricant and aggregating at the articulating surface.^[2] This may help protect cartilage and reduce pain.

Clinically, iPAAG is administered as a single 6 mL intra-articular injection.

Arthrosamid has demonstrated non-inferiority to hyaluronic acid (HA) for pain and function improvement in knee OA for at least one year, with similar safety profiles, though mild/moderate adverse device effects are more frequent with iPAAG. All of these side effects were classified as mild to moderate with no serious adverse events such as infection. ^[3] Retrospective data suggest modest advantages over corticosteroids at 6 months.^[4] Patient-reported outcomes indicate high rates of acceptable symptom states and minimal clinically important difference achievement at 3–6 months.^[3-5] The most recent data shows benefits from Arthrosamid may last for 5-10 years or longer.^[18]

Randomized controlled trials show that iPAAG provides similar symptomatic benefit to HA for at least one year after a single injection, with both treatments yielding significant reductions in WOMAC pain scores and no major safety concerns, though mild/moderate adverse device effects were more frequent with iPAAG.^[3] Retrospective cohort data suggest iPAAG may offer modest advantages over corticosteroids at 6 months, but its long-term superiority over HA is limited; by 12 months, differences between iPAAG and HA are not statistically significant.^[4] Observational studies also support sustained symptom improvement with iPAAG, but these require confirmation in larger randomized trials.^[5]

In contrast, multiple high-quality meta-analyses and network analyses consistently demonstrate that PRP—especially high-platelet concentration PRP—provides greater and more durable improvements in pain and function than HA at 6 and 12 months, with effect sizes exceeding minimal clinically important difference thresholds.^[6-9] PRP combined with HA may further enhance outcomes over PRP alone.^[10-11] The American Academy of Orthopaedic Surgeons guideline notes that PRP has a more prolonged effect than HA, though both are equivalent at 6 months; PRP is favored at 12 months, but may have a higher rate of mild adverse events.^[12]

In summary: iPAAG is as effective and may last longer than HA for knee OA, but high-dose PRP is generally superior to both for sustained pain and function improvement. PRP+HA may offer additional benefit. Long-term data for iPAAG are limited, and further head-to-head studies with PRP are needed.

The cost for one injection of Arthrosamid is between $4000 to $4500 CAD.

Injectable polyacrylamide hydrogel (iPAAG) is associated with a higher incidence of mild to moderate adverse device effects compared to hyaluronic acid (HA), but no serious adverse events have been reported. In a randomized controlled trial, 28.9% of patients receiving iPAAG reported adverse events, all of which were mild or moderate, versus 7.6% for HA, with no serious events in either group.^[3] These adverse events were typically local reactions such as pain or swelling.
For HA, the overall incidence of adverse events is low and comparable to placebo, with most reactions being transient and self-limited. Serious adverse events are rare and not statistically different from placebo or other injectables, and repeated courses of HA do not increase safety risk.^[13-15]
Platelet-rich plasma (PRP) injections have a complication rate similar to HA and corticosteroids, but significantly higher than placebo. Most PRP-related adverse events are mild or moderate and self-limiting, such as local pain or swelling, with no significant difference in serious adverse events compared to HA.^{[4, 16-17]}