Polyacrylamide Hydrogel Injection for Knee Osteoarthritis: A 6 Months Prospective Study

Objective: Intra-Articular (IA) injection of polyacrylamide hydrogel (PAAG) is a possible treatment for symptomatic Osteoarthritis (OA) of the knee. This study evaluated the efficacy and safety of a single injection of 6 ml intra-articular PAAG over 26 weeks.

Methods: Open-label study in patients with symptomatic and radiographically confirmed knee OA . Primary outcome was change in WOMAC pain after 13 weeks. Secondary outcomes were WOMAC stiffness and function subscales, Patient Global Assessment of disease impact (PGA) and proportion of OMERACT-OARSI responders. Follow-up time points were 4, 13 and 26 weeks.

Results: 49 patients (31 females) received PAAG, with 48 patients completing the 13 and 46 the 26 weeks assessments. Mean change in WOMAC pain after 13 weeks was -18.3 points [95% CI-23.4 to -13.3]; P<.0001 and at 26 weeks -20.8 points [95% CI -26.3 to -15.3]; P<0.0001 with similar benefits for WOMAC stiffness, physical function, and PGA. After 13 weeks 64.6% were OMERACT-OARSI responders and this was maintained at 26 weeks.. During the 13 weeks, 18 patients reported 23 adverse events, 13 of which were related to PAAG, none severe. Two serious adverse events, atrial fibrillation and gastrointestinal pain, were assessed as ‘not related’ to PAAG.

Conclusions: PAAG can be delivered in a single 6 ml injection and this non-randomized trial in patients with knee OA demonstrated beneficial clinical effects at 13 and 26 weeks. No serious adverse events were seen with PAAG. These encouraging results need to be confirmed in controlled studies.