Polyacrylamide hydrogel injections in knee osteoarthritis: A PROMs-based 24 month cohort study.

Background: The intra-articular polyacrylamide hydrogel (PAAG) injection known to be safe and efficacious in knee osteoarthritis (OA) patients. However, literature surrounding which patients would incur most benefit from PAAG is limited. We aim to identify patient factors that would allow PAAG to provide the most clinical benefit in knee OA patient. Methods: Knee OA patients were identified in clinics in Lincoln and London to engage in prospective cohort study. Patient factors were recorded and a course of PAAG was administered. Outcomes were Visual Analogue Score (VAS), Oxford Knee Score (OKS) and Lysholm scores taken from baseline till 24 months. Patients were further grouped based on number of scores that have reached Minimal Clinically Important Difference. Univariate and multivariate analysis were used to identify influence of patient factors on outcome scores and MCID, need for TKR(total knee replacement), and development of complications. Results: 314 knees (269 patients) with OA were treated with PAAG and followed up over 2 years. The patient factors that increased the odds of reaching MCID in all 3 scores by 24 months include being older (Exp B = 1·015, p = 0·041), a lower knee OA grade (Exp B = 0·576, p = 0·001), not having diabetes (Exp B = 2·204, p = 0·027), and having bilateral rather than unilateral knee OA (Exp B = 1·988, p = 0·021). 49 patients required TKR over the 2 years, with patients having higher-grade knee OA (b = 0·97, p < 0·001) more likely to have TKR. 155/314 knees developed complications. Conclusions: PAAG provided improvement in knee OA symptoms over 24 months, in older, non-diabetic patients with lower KL grades over 24 months. The absence of a control group and limited outcome measures should be considered. Further studies are warranted to validate efficacy, refine patient selection, and evaluate long-term impact.