**3. Methods and materials**

## **3.1 Participants**

Patients who were clinically diagnosed with PATB were recruited. Symptoms were determined to include medial knee pain when going downstairs or upstairs, rigidity for more than 1 h, sensitivity to compression on the tendon insertion area, and occasional local edema. All participants were randomly assigned into two groups—the US-guided injection group and the blind injection group. The randomization and allocation sequences were generated by using Microsoft Excel. Seven patients were dropped out to follow-up, and a total of 47 patients were finally analyzed (**Figure 1**). Patients who had knee OA (grade I–III Kellgren-Lawrence), pain in the medial aspect of the knee, and symptoms lasting for at least 3 months were included. These patients presented maximal tenderness over the PAB, not on the joint line or around the patella bone. The exclusion criteria were history of traumatic injury or mechanical derangement, surgical intervention, systemic inflammatory disorders, concomitant severe rheumatic disease, microcrystalline arthropathy, or fibromyalgia.

The study was carried out with permission from the institutional review board of our hospital. Informed consent was obtained from each subject for study participation, according to the ethical guidelines of the hospital after the subject fully understood the study's purpose and methodology.

**Figure 1.** *Study flowchart.*
