ObjectivesThe 12-month efficacy and safety of a novel bioresorbable fluid implant based on CM-chitosan for intra-articular injection was evaluated in knee osteoarthritis (OA) patients with predictive factors of failure to viscosupplementation.DesignThis pilot single-blind randomized controlled study was conducted in 104 patients with at least one of the following OA phenotypes: tricompartmental OA, patellofemoral involvement, K&L grade III or IV and/or body mass index >30 kg/m2. Non-inferiority and superiority of CM-chitosan (KioMedineVSone) in reducing pain were evaluated compared Hylan G-F 20 (Synvisc-One). Efficacy was evaluated using the WOMAC scores, OMERACT-OARSI responder rates, TKA eligibility and events, patient and physician satisfaction.ResultsAt 6 months post-injection, mean WOMAC pain reduction vs. baseline was 69.4 ± 25.5 % for the CM-chitosan group and 66.3 ± 26.15 % for the Hylan G-F 20 group (non-inferiority p = 0.096; 95 % CI -16.94 %, 7.02 %). At 12 months, significant symptomatic improvement in both groups, with clinically important differences in WOMAC pain reduction in favor of CM-chitosan, were observed, including in the subgroups of patients with patellofemoral OA (Δ 11.5 %), obese patients (Δ 21.7 %) and patients eligible for TKA at baseline (Δ 13.5 %). CM-chitosan showed a high response rate (93.8 %), as well as high patient (93.8 %) and investigator (90.6 %) satisfaction. No new safety signals were identified.ConclusionsIn this difficult-to-treat population, CM-chitosan was non-inferior to Hylan G-F 20, but did show clinically important, though not statistically significant, differences in pain reduction at 12 months. CM-chitosan was effective in improving OA symptoms and physical function for 12 months.