**2.3. Intervention**

The participants in both groups attended 5-week treatments. The experimental group received continuous US waves: intensity, 0.8 W/cm<sup>2</sup> ; 100% fill; carrier frequency, 1 MHz. The patients received a series of 10 treatments 2 times per week. The treatments were performed using a US 13 EVO Cosmogamma (Emildue, Italy). The patients lied in a supine position. The acoustic gel, that was applied, did not contain any pharmacologically active substance. The medial and lateral parts of the knee were treated with US applied in circular movements. To ensure the best absorption of the energy the probe was put at right angles. Each treatment session did not last longer than 10 minutes. During the treatment the patients received neither any anesthetic nor other physical actions. No adverse events were observed during the treatment. The same therapist made US to all the participants.

The control group received ESWT − 1000 pulses during the first treatment, 1500 during the second and the third treatments, and 2000 during the fourth and the fifth treatments, respectively (pressure, 2.5 bar; frequency, 8 Hz; energy density, 0.4 mJ/mm<sup>2</sup> ). The patients received 5 ESWT treatments once per week. The treatments were performed using a Rosetta ESWT (CR Technology, Korea). The patients were placed in a supine position with the affected knee unbent or flexed at 90°, and an acoustic gel that did not contain any pharmacologically active substance was applied. The shockwave probe was held stationary on a trigger point around the knee or at the patellofemoral and tibiofemoral borders of the target knee, avoiding direct placement on the peroneal nerve or vessel. Each treatment session did not exceed 10 minutes. During the treatments, the patients did not receive any other physical method. No adverse events were observed during the treatment. The same therapist made ESWT to all the participants.

All of the treatments were performed at the Physiotherapy Outpatient Department of the Regional Hospital in Zywiec, Poland. Once a week for 5 weeks, the treatments were administered by an independent researcher who was not involved into this study. The same physiotherapist with a postgraduate degree in physiotherapy and 10 years' experience provided all the interventions to both (the experimental and the control) groups, and remained blind to primary and secondary outcome measures throughout the trial. The independent researcher analyzed the results/data also being blind to all of outcome measures throughout the trial.
