**2. Method**

## **2.1. Design**

It was a randomized trial with concealed allocation, assessor blinding, and intention-to-treat analysis. The participants with knee OA were assessed for eligibility by an independent physician who was not involved into the study. The randomization into an experimental group (US) and a control group (ESWT) with a 1:1 ratio was generated by permuted block randomization using the website www.random.org. The randomization was achieved by having the participant selected one from 60 sealed opaque envelopes, each containing a group allocation, which had been prepared and shuffled by an independent investigator who was not involved into the recruitment or assessment of the participants. The researchers responsible for assessing the outcomes and analyzing the data were blinded to the type of the treatment procedure. To keep the assessors blinded the participants were reminded before each measurement not to reveal the nature of their treatment. The participants were considered to be unaware of the group allocation because they were informed about the existence of two intervention groups but not about the study hypothesis. The data were obtained at baseline and 5 weeks later (immediately after the intervention period).
