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. Conclusion Ultrasound detected suprapatellar effusion predicts reduced efficacy of HA injection in knee OA