Effect of low-intensity long-duration ultrasound on the symptomatic relief of knee osteoarthritis: A randomized, placebo-controlled double-blind study

Abstract

Background: Wearable long-duration low-intensity ultrasound is an emerging non-invasive and non-narcotic therapy for the daily treatment of musculoskeletal pain. The aim of this randomized, double-blind, placebo-controlled study was to examine whether long-duration low-intensity ultrasound was effective in treating pain and improving function in patients with knee osteoarthritis. Methods: Ninety patients with moderate to severe knee pain and radiographically confirmed knee osteoarthritis (Kellgren-Lawrence grade I/II) were randomized for treatment with active (n=55) or placebo (n=35) devices applied daily to the treated knee. Investigators and subjects were blinded to treatment groups. Ultrasound (3MHz, 0.132W/cm2, 1.3W) was applied with a wearable device for 4h daily for 6weeks, delivering 18,720J per treatment. The primary outcome was change in pain intensity (numeric rating scale) assessed prior to intervention (baseline) and after 6weeks. Secondary outcomes of functional change were measured at baseline and after 6weeks using the Western Ontario McMaster Osteoarthritis Questionnaire (n=84), along with range of motion (flexion, extension) and isometric muscle strength (flexion, extension and rotation) tests on the injured knee in a small pilot subset (n=17). Results: The study had a 93% retention rate, and there were no significant differences between the groups regarding demographic variables or baseline outcome measures. Patients treated with active therapy observed a significant mean NRS pain reduction over the 6-week study of 1.96 points for active (p<0.0001), compared with a 0.85 points reduction for placebo (p=0.13). The functional score was also significantly improved by 505 points for the active group over the 311-point improvement for placebo group compared to baseline (p=0.02). In the pilot subset evaluated, rotational strength increased from baseline to 6weeks (3.2N, p=0.03); however, no other measures were significant. Conclusions: Long-duration low-intensity ultrasound significantly reduced pain and improved joint function in patients with moderate to severe osteoarthritis knee pain. The clinical findings suggest that ultrasound may be used as a conservative non-pharmaceutical and non-invasive treatment option for patients with knee osteoarthritis. Additional research is warranted on non-weight bearing joints of the musculoskeletal system as well as extended treatment time frames and follow-up. Trial registration: NCT02083861, registered 11 March 2014, https://clinicaltrials.gov/ct2/show/results/NCT02083861