Effect of ultrasound therapy for knee osteoarthritis: a meta-analysis of randomized, double-blind, placebo-controlled clinical trials

Objective: To perform a meta-analysis of randomized, double-blind, placebo-controlled clinical trials to separately assess the effect of continuous ultrasound (US) therapy and pulsed ultrasound therapy with low frequency for decreasing pain and improving physical function on people with knee osteoarthritis. Data sources: A systematic review (to April 2015) is conducted without language limits in PubMed, OVID and Medline database. Study selection: All trials were selected for adequate randomization, double-blind, follow-ups and control group involving patients diagnosed knee OA. Data extraction: 6 trials were excluded for the reasons below: (1) Without control. (2) Incomplete data. (3) Single blind. Data synthesis: After reviewed by Pubmed, OVID and Medline database, six clinical trials of 417 patients were included. Compared to sham US, continuous US reduced pain on a 10 cm visualanalogue- scale (VAS) [Standardized Mean Difference (SMD) (95% confidence interval (CI)) = -0.58 (-0.91, 0.25), P = 0.0006], while pulsed US reduced pain [SMD 95% confidence interval (CI) = -1.06 (-1.46, -0.65), P<0.001]. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function subscale score of continuous US were improved [SMD 95% confidence interval (CI) = -3.74 (-8.16, -0.67), P = 0.10] compared to sham US. Conclusion: These results demonstrated that both continuous and pulsed Ultrasound therapy could efficiently reduce pain and improve physical function in people diagnosed with knee osteoarthritis. The pulsed US seemed more effective in these aspect to improve patients' life quality.