Polyacrylamide gel versus hyaluronic acid for the treatment of knee osteoarthritis: a randomised controlled study

OBJECTIVES: To assess non-inferiority of intra-articular injectable polyacrylamide hydrogel (iPAAG) to hyaluronic acid (HA) on symptomatic benefit in individuals with knee osteoarthritis (OA).

METHODS: This randomised, controlled, multi-centre trial recruited adults with symptomatic and radiographic knee OA from 3 clinical rheumatology sites in Denmark; two private clinics and one public hospital department. Participants were randomised 1:1 to receive a single intra-articular 6 mL injection of either HA or iPAAG on an outpatient basis. Primary outcome was change from baseline in WOMAC pain subscale after 26 weeks. Secondary outcomes were changes from baseline in WOMAC stiffness and physical function subscales, patients' global assessment of disease impact, EuroQoL-5D-5L, and proportion of positive OMERACT-OARSI responders after 26 and 52 weeks.

RESULTS: 239 adults were randomised: 120 to HA and 119 to iPAAG. For the primary outcome, the least squares mean changes in WOMAC pain were -14.8 (95% CI: -18.0 to -11.7) for HA and -18.5 (95% CI: -21.7 to -15.4) for iPAAG; group difference: 3.7 (95% CI: -0.7 to 8.1). The lower boundary of the 95% CI respected the pre-specified non-inferiority margin of 9 WOMAC pain points. No statistically significant differences were observed for the secondary outcomes. For HA, 9 participants (7.6%) reported 13 adverse device effects (ADEs). For iPAAG, 35 participants (28.9%) reported 41 ADEs. All ADEs were mild/moderate, with no serious ADEs reported.

CONCLUSIONS: iPAAG was found to be as effective and safe as HA for treatment of knee OA symptoms for at least 1 year after a single injection.