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Three-year follow-up from a randomised controlled trial of a single intra-articular polyacrylamide hydrogel injection in subjects with knee osteoarthritis
H. Bliddal1, J. Beier2, A. Hartkopp3, P.G. Conaghan4, M. Henriksen5
- The Parker Institute, Bispebjerg Frederiksberg Hospital, University of Copenhagen, Denmark. henning.bliddal@regionh.dk
- Gigtdoktor, Odense, Denmark.
- A2 Rheumatology and Sports Medicine, Holte, Denmark.
- Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds & NIHR Leeds Biomedical Research Centre, UK.
- The Parker Institute, Bispebjerg Frederiksberg Hospital, University of Copenhagen, Denmark.
CER18916
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PMID: 41487107 [PubMed]
Received: 14/05/2025
Accepted : 24/10/2025
In Press: 11/12/2025
Abstract
OBJECTIVES:
A randomised controlled trial demonstrated comparable efficacy and safety of a single 6 mL intra-articular (IA) injection of 2.5% polyacrylamide hydrogel (2.5% iPAAG) versus hyaluronic acid (HA) over one year in adults with moderate-to-severe knee osteoarthritis (OA). This study evaluated the long-term effectiveness and safety of 2.5% iPAAG.
METHODS:
This 3-year extension of a randomised controlled trial (RCT) (ClinicalTrials.gov Identifier: NCT04045431) followed participants who received a single 6 mL IA injection of 2.5% iPAAG. Outcomes included changes from baseline to year 3 in WOMAC pain, stiffness, and physical function subscales (0–100 scale) and patient global assessment (PGA) of OA impact. Safety was assessed up to year 3.
RESULTS:
A total of 119 participants received IA 2.5% iPAAG. After one year, 91 participants (44 females) entered the extension study, and 75 completed 3-years of follow-up. At year 3, the mean change in WOMAC pain was -13.1 (95% CI: -17.9 to -8.4; p<0.0001). Between the 1-year and 3-year visits, fifty adverse events (AEs) were reported by 36 participants (29.8%), none of which were assessed as related to 2.5% iPAAG.
CONCLUSIONS:
A single 6 mL IA injection of 2.5% iPAAG appears to be safe and effective in providing sustained symptom relief for up to 3 years in individuals with knee OA.
