Effectiveness and Functional Outcome of Polyacrylamide Hydrogel Injection for Knee Osteoarthritis

The increasing societal and economic burden of osteoarthritis is well known, with over 6% of the current adult population suffering from symptomatic knee osteoarthritis. Mild to moderate knee arthritis has few effective solutions. Repeated steroid injections have been proven to be progressively ineffective and detrimental to large weight-bearing joints. Polyacrylamide hydrogels are bio-inert, non-degradable and highly viscous. The gel initially produces a low-friction environment before integrating into the synovium and forming a neo-intima that produces an anti-inflammatory effect by preventing pro-inflammatory macrophages from migrating from the synovium. Here, we present our short-term results, including a UK satisfaction survey, and complications from a study conducted across various locations in the United Kingdom. To date, 204 patients have received hydrogel injections, with 58 full data sets available from patients aged 41–89 years with Kellgren-Lawrence grade 2–4 knee osteoarthritis. Baseline and 3-month data were presented, showing significant improvements: VAS Pain decreased from 68 to 41 (p<0.0001), OKS improved from 28 to 17 (p<0.0001), WOMAC Pain reduced from 60 to 34 (p<0.0001), and WOMAC Total decreased from 56 to 35 (p<0.0001). An anonymous survey of 95 patients from six UK surgeons revealed that 68% “would recommend this treatment,” and 62% were “satisfied.” Of the 204 patients treated locally, two re-attended. One patient underwent joint aspiration at three weeks, and another developed a severe soft tissue reaction requiring washout, muscle debridement, and soft tissue coverage. Both had negative aspirates for infection but elevated inflammatory markers. Initial short-term results following hydrogel injections are extremely promising. Patient satisfaction is good when compared to the 72–86% satisfaction reported following total knee replacement. Further understanding of the rare post-injection inflammatory reaction is essential before more widespread use of hydrogel injections.