Effect of ultrasound-detected synovitis on therapeutic efficacy of hyaluronic acid injection for symptomatic knee osteoarthritis

Objective: To determine whether ultrasound (US)-detected synovitis affects the therapeutic efficacy of hyaluronic acid (HA) injection for treating knee OA. Methods: Patients with symptomatic knee OA were recruited. All the patients received HA injection two times at 2-week intervals. Clinical assessments were performed using a visual analogue scale (VAS) and the Western Ontario and McMaster Universities OA Index (WOMAC) at baseline and 1 and 6 months after treatment. Imaging evaluation was based on complete knee US examination and the Kellgren-Lawrence grading. Suprapatellar synovial fluid (SF) depth, synovial hypertrophy (SH) and vascularity were measured through US. Results: In total, 137 patients who fulfilled the inclusion criteria were included in the analysis. All patients demonstrated improvement in VAS and WOMAC scores at 1 and 6 months after treatment (P < 0.001). Moreover, regression model-based analysis revealed significant associations of SF depth with the VAS and WOMAC scores in all patients. Each centimetre increase in the effusion diameter was associated with a decrease in the 1-month post-treatment VAS improvement percentage (15.26; 95% CI: 0.05, 29.5; P = 0.042) and 6-month post-treatment WOMAC improvement (37.43; 95% CI: 37.68, 50.69; P < 0.01). However, SH and vascularity were not significantly associated with VAS or WOMAC scores.