Concurrent Imaging and Clinical Study of the Efficacy of Hyaluronic Acid Injection for Knee Osteoarthritis: A Synovial Membrane Investigation with Ultrasound Imaging

We investigated whether hyaluronic acid (HA) injections can ameliorate ultrasound-detected synovitis in knee osteoarthritis (OA). We recruited 103 patients with symptomatic knee OA and ultrasound-detected synovitis and performed two ultrasound-guided fluid drainage procedures, followed by the administration of a low-molecular-weight HA injection (2.5 mL) in the subpatellar bursa, at a 2-week interval. Knee ultrasound imaging evaluations were performed before injection (baseline) and at 1 and 6 months after the second injection and included the measurements of synovial vascularity by using color Doppler ultrasound, synovial fluid depth over the suprapatellar bursa (SF), and synovial hypertrophy (SH). Initial clinical assessments included a visual analog scale (VAS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). VAS scores decreased significantly at both 1-month and 6-month evaluations (p < 0.001). WOMAC scores also significantly decreased at 1 month (p < 0.001), but not at 6 months (p = 0.23). The ultrasound parameters did not significantly change, except color Doppler grading, which tended to decrease at the 6-month evaluation (p = 0.059). Our findings revealed that two ultrasound-guided HA injections following fluid drainage improved pain and knee function but did not considerably influence imaging-detected synovitis in patients with knee OA.