Arthrosamid® has proven to be a long-term and effective treatment for patients with knee osteoarthritis. Clinical studies show that 80% of treated patients experience significant improvement in pain reduction, mobility and function. These improvements are maintained for years after the initial injection (up to 5 years).
Arthrosamid® is an injectable hydrogel consisting of 97.5% water and 2.5% crosslinked polyacrylamide. Treatment is via six separate 1 ml injections, where the hydrogel is introduced into the synovial space. This leads to the following physiological changes:
✔ Tissue growth and thickening – After injection, synovial tissue grows in the open structure of Arthrosamid®, thickening and strengthening the joint capsule.
✔ Permanent presence – Arthrosamid® is not resorbed or degraded, but remains permanently present in the tissue.
✔ S afety and long-term use – More than 1,700,000 treatments have been performed worldwide with no permanent adverse side effects.
✔ Knee replacement possible after treatment – In a 10-year retrospective study of 120 patients, 56% did not need a knee replacement after 10 years. For the remaining patients who received a prosthesis, there were no side effects related to the hydrogel.
✔ Improved tissue elasticity – Clinical studies show a 15% increase in synovial tissue elasticity, normalizing joint function.
✔ Reduced pain signals – Improved elasticity reduces nocisensory pain perception, leading to reduced pain symptoms.
✔ Anti-inflammatory effect – Arthrosamid® thickens synovial tissue and creates a natural barrier to inflammatory cells, reducing inflammatory activity, improving mobility and reducing pain symptoms.
✔ Healthier synovial fluid – Recent research (2025) shows that patients with a positive response have more hyaluronic acid and less interleukin-6 (IL-6) in their synovial fluid, indicating reduced pro-inflammatory activity.
The biochemical and mechanical changes following treatment with Arthrosamid® contribute to a healthier joint and possibly a delayed progression of osteoarthritis. This makes Arthrosamid® a promising long-term option in the treatment of knee osteoarthritis.
Statistically significant reduction in pain maintained at 5 years.1
Polyacrylamide Hydrogel for Knee Osteoarthritis: 5-Year Results from a Prospective Study
Presented at WCO-IOF-ESCEO 2025.
Link: https://www.wco-iof-esceo.org/download/2025/abstract-book page 562
Authors: H. Bliddal et al.
This research evaluated the long-term efficacy and safety of a single 6 mL intra-articular injection of polyacrylamide hydrogel (iPAAG) for treating knee osteoarthritis (OA). The study followed 49 participants (average age 70 years) over five years across multiple sites in Denmark. Outcomes were assessed using the WOMAC and Patient Global Assessment (PGA) measures.
Results showed a statistically significant reduction in pain scores over five years, with similar improvements observed in sensitivity analyses. The treatment maintained clinical effectiveness and was well tolerated, with no treatment-related serious adverse events reported.
The findings support iPAAG as a long-lasting, 5 years, non-surgical intervention for knee OA.
Acknowledgments This study was sponsored by Contura International A/S.
iPAAG: injectable polyacrylamide hydrogel
Title 10-Year Safety Follow-Up of Intra-Articular 2.5% Polyacrylamide Hydrogel (iPAAG) in Knee Osteoarthritis (OA)
Presented at: WCO-IOF-ESCEO 2025, Rome
Authors: H. Bliddal, et all.
Link: httpwww.wco-iof-esceo.org/download/2025/abstract-book page 58 OC11
This long-term observational study assessed the safety of intra-articular 2.5% polyacrylamide hydrogel (iPAAG) in knee osteoarthritis (OA) patients over a follow-up period of 7 to 14 years(mean: 9.92 years). The study included 61 patients (89 treated knees), with an average injection age of 64 years. Safety outcomes showed no significant adverse events (AEs) related to iPAAG, including no allergic reactions, infections, or systemic effects.
Among treated knees, 43.8% underwent knee replacement surgery, with an average time to replacement of 3.4 years. 56.2% Surgical complications were minimal and unrelated to iPAAG. Findings support iPAAG as a long-term, well-tolerated non-surgical option for OA, reassuring healthcare providers about its safety profile and potential to delay knee arthroplasty; 56.2% didn’t receive any knee replacement in 10 years after the one single treatment.
Long-term results after iPAAG indicated a favorable safety profile of the product. Surgical records from subsequent knee replacements gave no indications of unusual adverse reactions.
3 YEARRESULTS FROM A PROSPECTIVE STUDY OF POLYACRYLAMIDE HYDROGEL FOR KNEE OSTEOARTHRITIS
Authors: M. Henriksen1, et all.
Link: https://www.oarsijournal.com/article/S1063-4584(23)00647-7/fulltext
This prospective, multicenter study in Denmark evaluated the long-term effects of a single 6 mL intra-articular injection of Arthrosamid® for knee osteoarthritis (OA). Initially planned for one year, the study was extended to five years, with participants re-consenting for continued follow-up. A total of 49 participants (average age ~70 years) were treated, with follow-up visits scheduled over three years.
Outcomes were assessed using WOMAC pain, stiffness, and function subscales, as well as Patient Global Assessment (PGA). Statistical analyses showed significant improvements in OA symptoms over three years, with clinically relevant reductions in pain scores. Sensitivity analyses confirmed the consistency of results.
Adverse events (AEs) were reported throughout the study, including 19 new events between the second and third years. None were linked to the treatment, and the most frequent AE was Covid-19 infection. Overall, Arthrosamid® demonstrated continued effectiveness and a strong safety profile over three years.
A Mechanistic and Clinical study of intra-articular Arthrosamid for knee osteoarthritis
Presented at the ISAKOS Congress 2025
Author(s):Sharon Owen, et all.
This study investigated the clinical effectiveness and potential mechanism of action of Arthrosamid®, a biocompatible injectable hydrogel, for knee osteoarthritis (OA). A total of 62 patients (68 knees) received a single 6 mL injection and were followed for up to 12 months. Primary outcomes were measured using the WOMAC index, with secondary outcomes including KOOS scores and adverse events.
Results showed a significant improvement in WOMAC and KOOS scores over time, indicating strong clinical effectiveness. The overall response rate at six months was 76%. Synovial fluid analysis suggested an anti-inflammatory mechanism of action and increase of HA among responders, though further bioinformatic analysis is ongoing. Adverse events were primarily mild, including arthralgia and swelling.
Findings support Arthrosamid® as a promising non-surgical option for managing knee OA symptoms.
A randomized study of one-year performance of polyacrylamide hydrogel (iPAAG) vs. hyaluronic acid.
Use of a 2.5% Cross-Linked Polyacrylamide Hydrogel in the Management of Joint Lameness in a Population of Flat Racing Thoroughbreds: A Pilot Study; de Clifford LT, et al. J Equine Vet Sci. 2019; 77: 57-62
Link: https://www.sciencedirect.com/science/article/abs/pii/S0737080618307615
Intra-articular 2.5% polyacrylamide hydrogel for the treatment of knee osteoarthritis: an observational proof-of-concept cohort study;1Henriksen M, et al. Clin Exp Rheumatol. 2018;36 (6):1082-1085
