Efficacy of intra-articular 3% polyacrylamide hydrogel in the treatment of knee osteoarthritis: findings from the 24-month follow-up

Background. Osteoarthritis (OA) is among the most common chronic diseases and leading causes of disability globally. It places a significant burden on healthcare systems and adversely effects patients’ quality of life. The short-term efficacy of most therapies has driven the search for new treatment approaches in OA. The aim of the study — to evaluate the duration of response to intra-articular injections of 3% polyacrylamide hydrogel in patients with knee osteoarthritis, factors influencing response duration, and the efficacy and safety of repeated treatment. Methods. In a 6-month placebo-controlled randomized trial, patients with Kellgren-Lawrence (1957) grades II-III knee OA were randomly assigned to receive either intra-articular injections of 8.0 ml polyacrylamide hydrogel (PAAG) or placebo. Subjects from the PAAG group could roll over to the open-label extension (OLE) and if clinically indicated received the second course of PAAG. A survey of OLE participants was conducted at 24 months post-treatment. The efficacy of PAAG was assessed by the WOMAC index, a pain VAS, subjective evaluations of treatment outcomes by both the patient and the researcher, as well as by the daily requirement for paracetamol and nonsteroidal anti-inflammatory drugs. Safety was assessed by adverse events (AEs) monitoring. Results. At month 6, PAAG was superior to placebo in reducing the WOMAC-T score (-604.44 versus -450.61, p = 0.011). Within 6-9 months of initial treatment, 26% of patients who had significantly higher baseline WOMAC scores and body weight required a repeat course of PAAG. In these patients, the mean reduction in WOMAC-T from baseline to month 12 was -361.33 and -795.64, respectively, compared to -688.53 with one course of PAAG (p = 0.107). At the end of the 24-month follow-up, the mean WOMAC-T reduction reached 714.13 versus -716.65 in the single-course group compared to two-course group. The majority of AEs were mild, and there were no serious AEs reported. Conclusion. Polyacrylamide hydrogel has demonstrated a favorable safety profile and sustained symptomatic benefit over 2 years. In patients with risk factors for disease progression a repeated course is recommended.