**1. Introduction**

Osteoarthritis (OA) is a chronic and degenerative disease and is considered to be one of the most common musculoskeletal disorders. Joints found in our body can be affected by OA. All

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the patients with OA have almost the same symptoms, including pain, stiffness, articular instability, limitation of motion and physical activity, and muscle weakness [1, 2]. Physiotherapy is one of the treatments that provides effective nonpharmacological interventions for people with knee OA, and procedures prescribed by physiotherapists are considered to be important and to play a fundamental role in patients' treatment. The most common types of electrotherapy are ultrasound (US), transcutaneous electrical nerve stimulation (TENS), and now more often appearing extracorporeal shock wave therapy (ESWT). US, as a noninvasive treatment is used to create a controlled, microtrauma to local affected tissue in order to stimulate a healing response and microvascularization [3, 4]. The first use of ESWT was not for musculoskeletal disorders but to break up kidney stones. It was a coincident that someone noticed an osteoblastic response pattern during studies at animals in the 1980s [5]. Recently, ESWT has been used for pain relief and musculoskeletal disorders' treatment. It turned out that ESWT is also a noninvasive treatment, and the effectiveness of this method is comparable to surgery. It has not yet been fully explained how it exactly works, but it probably involves microdestructions—the application of ESWT causes microbreaks in avascular or poorly vascularized tissue, thus stimulating appropriate revascularization and stem cell growth. It also induces the release of enzymes, which affect nociceptors, resulting in localized analgesia, giving the significant reduction of activity limitations and short duration of the treatment [6].

Despite the advances in the treatment, there is lack of comparative studies on the effects of US and ESWT in patients with knee OA. Therefore, the purpose of this study was to evaluate the effects of US versus ESWT protocol on pain measured by visual analogue scale (VAS), and on perceived health measured by WOMAC [7, 8] in men suffering from bilateral knee OA.

In our study we took hypothesis: there are differences between US and ESWT in reducing of pain, and improving perceived health in men suffering from bilateral knee OA.

Therefore the research question was

**1.** Is US more effective than ESWT on pain and perceived health in men with bilateral knee OA?
