Effects of therapeutic ultrasound in patients with knee osteoarthritis: A systematic review and meta-analysis

Background: Therapeutic ultrasound (US) is a treatment for knee osteoarthritis (KOA), but its efficacy and safety are unclear. The objective of this study is to quantify the effect of US on pain relief and function recovery in KOA, and to analyze the US treatment duration and parameters on treatment outcome. Methods: We searched PubMed, MEDLINE, EMBASE, Google Scholar, Cochrane databases and ClinicalTrials.gov databases up to April 7, 2023. RCTs that compared the efficacy of therapeutic US with the control in KOA were included in the study, and the methodological quality of the trials was assessed using the Cochrane Risk of Bias tool. Results: Twenty-one RCTs (1315 patients) were included. US had a positive effect on visual analog scale (VAS) (SMD = -0.64, 95 % CI [-0.88, -0.40], I2 = 71 %) and Western Ontario and McMaster Universities (WOMAC) total scale (SMD = -0.45, 95 % CI [-0.69, -0.20]; I2 = 67 %). Pulsed US with an intensity <= 2.5 W/cm2 reduced visual analog scale (VAS), and differed in sessions (24 sessions (SMD = -0.80, 95 % CI [-1.07, -0.53], I2 = 0 %) vs 10 sessions (SMD = -0.71, 95 % CI [-1.09, -0.33], I2 = 68 %)). For pulsed US, a duration of treatment of 4-8 weeks (SMD = -0.69, 95 % CI [-1.13, -0.25], I2 = 73 %) appeared to be superior to <= 4 weeks (SMD = -0.77, 95 % CI [-1.04, -0.49], I2 = 0 %) for reducing visual analog scale (VAS). No US treatmentrelated adverse events were reported. Conclusion: Therapeutic US may be a safe and effective treatment for patients with KOA. The mode, intensity, frequency, and duration of US may affect the effectiveness of pain relief. Pulsed US with an intensity <= 2.5 W/cm2, 24 sessions, and a treatment duration of <= 4 weeks appears to have better pain relief.