A three-year chitosan injection regimen is associated with sustained quality of life improvements in early knee osteoarthritis patients: a five-year retrospective cohort study

Abstract Background Knee osteoarthritis (OA) is a leading cause of disability worldwide. Current treatments often offer only short-term symptom relief without slowing disease progression. Chitosan, a biocompatible polymer with anti-inflammatory and lubricating properties, has shown promise in short-term studies, but long-term data is lacking. This study compared the five-year outcomes of a three-year intra-articular chitosan injection regimen plus conventional therapy (CT) against CT alone in patients with early knee OA. Methods In this single-center, retrospective cohort study (March 2018–February 2019), we screened 104 patients with bilateral symptomatic early-stage knee osteoarthritis. Of these, 63 completed the study (Group A: chitosan + CT, n = 31; Group B: CT alone, n = 32). Group A received three biweekly 2 mL chitosan injections annually for three years, alongside a structured CT program (including lifestyle education, weight management, exercise, and medication). We assessed pain (VAS), joint function (WOMAC), and quality of life (SF-36) at baseline and five years. Results Baseline characteristics were similar between groups. At five years, Group A had significantly lower pain scores (VAS: 5.33 vs. 6.23; p < 0.001) and showed less worsening in all WOMAC subscales (pain, stiffness, physical function; all p < 0.05). Although all SF-36 domains declined over time, Group A maintained significantly higher scores in seven of eight domains, including physical function, bodily pain, and mental health (all p < 0.05). No serious injection-related adverse events occurred. Conclusion For patients with early knee OA, a three-year course of intra-articular chitosan injections combined with conventional therapy was associated with better long-term outcomes in pain, function, and quality of life after five years compared to conventional therapy alone. These findings support further investigation in prospective trials.