Early Efficacy of Intra-Articular HYADD® 4 (Hymovis®) Injections for Symptomatic Knee Osteoarthritis

Purpose  The aim of the study was to evaluate the clinical effects of HYADD® 4, an hydrogel based on a hyaluronic acid derivative, in patients with symptomatic knee osteoarthritis, on symptoms, and joint function. Methods  This retrospective study of patients with Kellgren-Lawrence grade II to IV knee osteoarthritis (American College of Rheumatology criteria) enrolled patients who had received two infiltrations of HYADD® 4, (24 mg/3 mL) 1 week apart, and evaluated: pain at rest, pain with movement, change in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score; change in nonsteroidal anti-inflammatory drugs (NSAIDs)/acetaminophen use; satisfaction with therapy; tolerability. Study duration was 6 months for all predefined endpoints, with a 6-month extension for pain symptoms only. Results  After 6 months, all predefined endpoints were evaluable in 698 of 937 enrolled patients (74.5%). Mean WOMAC scores were reduced by 56.3% from baseline ( p  < 0.05). NSAIDs/acetaminophen use ≥2 times/week (48.8% of patients at baseline) was substantially reduced after 1 month and was 19.6% after 6 months. After 6 months, 85.6% of patients were satisfied about efficacy. There were no significant adverse effects. The effect on resting pain was rapid, strong, and lasting: reduction from baseline was 45.1% at 1 month ( p  < 0.05), 56.8% at 6 months ( p  < 0.05), and 53.6% at 12 months ( p  < 0.05). Pain on moving was reduced by 47.4% after 6 months ( p  < 0.05) and 46.0% after 12 months ( p  < 0.05), results at 6 and 12 months were similar. Conclusion  HYADD® 4 is a new-generation hyaluronic acid with distinctive viscoelastic and rheological properties. In patients with mild-to-severe knee OA (Kellgren-Lawrence grades II-IV), two consecutive infiltrations 1 week apart reduced WOMAC scores and NSAIDs/acetaminophen consumption for at least 6 months. In a subpopulation ( n  = 106), efficacy on pain lasted approximately 12 months. Adverse events were reported in 11.2% of patients; the most frequent were arthralgias. No cases of allergic reactions or systemic effects were recorded. Level of Evidence  Level IV, retrospective case series.