## 2 Materials and Methods  
Patients with long-lasting shoulder pain (at least 3 months), already diagnosed by a rheumatologist with SAPS, treated with physical therapy in an outpatient rehabilitation clinic and who were followed-up 15 days after the completion of physical therapy program were included in this study. We excluded patients with systemic inflammatory rheumatic diseases, decompensated heart failure, neurologic deficits, spinal disorders, history of shoulder or neck surgery, referred pain. Patients who received analgesics or steroid injections for their shoulder pain were also excluded. Written informed consent was obtained from all participants that accomplished inclusion criteria and agreed to participate in the study [14]. This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of the University (approval number 32035/0-1/22.07.2020). The study was registered as a non-randomized trial, with no IRCT20200422047172N1. Data were collected from the patients' records, including socio-demographic data (age, gender, height, weight and occupation), the affected shoulder (left or right), diagnosis, rehabilitation treatment and outcome assessments. Based on the type of the electrotherapy procedure prescribed in addition to the rehabilitation exercises, the patients included in the study were divided into two groups. The patients in Group 1 (\(n\) = 22) had a total of 10 sessions of MLS laser therapy associated with physical therapy exercises. The duration of laser treatment was five minutes for each session. The MLS laser therapy was applied using a Mphi system (ASA Srl, Arcugnano, Italy) on the anterior and posterior part of the shoulder (Figure 1), with a laser pulse repetition frequency of 700 Hz, a dose of 2.8 Joule/cm\({}^{2}\), an intensity of 50%, per 5 min. The second group (\(n\) = 25) received ten US therapy sessions for the affected shoulder, as well as TENS (20 min) (Figure 2), and physical therapy exercises. Continuous ultrasound was applied using circular movements at an intensity of 1 W/cm\({}^{2}\), and 1 MHz, for 3 min. In addition, TENS was applied using a frequency of 90 Hz, symmetric biphasic, for 20 min. All classical electrotherapy applications were performed using the Chattanooga Intellect Neo combined device. Initially, all patients performed Codman exercises, passive range of motion exercises, glide mobilization techniques and stretching exercises. Further, as the pain decreased and the mobility of the affected shoulder increased, active range of motion exercises, isometric and resistive exercises were added to the therapeutic program. The above-mentioned exercises have been performed once a day with 10 repetitions and applied five times a week, for three weeks. The patients were evaluated before treatment and 15 days after the end of treatment. Pain was evaluated using a VAS (visual analog scale), functional activity was evaluated using the Constant Shoulder Score (CSS) and the Shoulder Pain and Disability Index (SPADI). In VAS assessment, the degree of pain at rest and during activity was evaluated on 10-cm scale, with 0 indicated \"no pain\" and 10 indicated \"worst pain\". SPADI is a self-administered questionnaire with two subscales-pain and disability. Each question quantifies the pain felt and the degree of disability perceived at a certain movement/in carrying out a certain activity, through a numerical representation between 0 and 10, similar to completing the VAS scale. The final score is calculated, being subsequently divided by the number of questions and the final percentage result (%) represents the existing level of pain and functional disability. The higher the score, the greater the pain and functional impairment [15; 16]. Recently, several studies reported that the reliability  
Figure 1: Multiwave Locked System (MLS) application. coefficients of SPADI is good with an intraclass correlation coefficient of \(\geq\)0.89.