Patient-reported outcomes of intra-articular hyaluronic acid for osteoarthritis of the knee: a prospective and multicentric case series

Background: In the present study, patients with symptomatic knee osteoarthritis (OA) were treated with single intra-articular injection of a high molecular weight, non-cross-linked hyaluronic acid (HA), highly concentrated (2%) and associated with sorbitol (4%). The aims of this study were to (1) evaluate clinical outcome after 6 months, (2) evaluate clinical outcomes after 12 months and (3) evaluate clinical outcomes according to OA grade. Hypothesis of the study was that a single intra-articular injection of this HA associated with sorbitol leads to a significant clinical improvement within 6 months in patients with early or moderate knee OA. Materials and methods: A total of 77 patients were enrolled in this prospective multicentric study. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score was recorded at baseline and at months 1, 3, 6 and 12 following the intra-articular injection. Moreover, a stratified analysis of all WOMAC items following the OA grade was performed for both groups of patients, one with low (grade I–II according to Kellgren–Lawrence classification) and another with moderate OA grade (grade III according to Kellgren–Lawrence) and the differences between groups were evaluated. Results: Seventy-three patients completed the 12 months follow-up. Pain, stiffness, functional limitation and total scores were significantly reduced at 1, 3 and 6 months (p < 0.05), but not at 12 months. Stratified analysis of all subscores according to OA grade showed that pain, functional limitation and total score decreased at 1, 3, 6 and 12 months (p < 0.05) in both groups. Stiffness was the only item that decreased significantly at 1, 3 and 6 months but not at 12 months in both groups. All subscore values were significantly lower in the group of patients with low OA grade compared to the one with moderate OA grade. No adverse events were reported. Conclusion: At 6 months after a single intra-articular injection of a high molecular weight, non-cross-linked HA associated with sorbitol, WOMAC scores decreased significantly. Clinical benefits were observed both in patients with low and in those with moderate OA grade, with better results in the first group.