**1. Introduction**

Therapeutic ultrasound (US) is performed in physiotherapy to treat a variety of inflammatory and post‐traumatic diseases. Most of their effects depend on the induction of local thermal increases, which elicit local vasodilatation and toxic substances washout; however, specific and quantitative effects are often misconsidered in physiotherapy units. Moreover, despite its widespread use in rehabilitative practice and a large number of studies, low scientific, statistically assessed evidences of therapeutic US effectiveness are available. As a matter of fact, details about the treatment modalities and the way in which the patients' feedback was collected are often missing. The chapter will be focused on the following points:

(1) Physical bases, technical approach and quality assurance of ultrasonic equipment: tech‐ nological development and wide use of US within the patient's rehabilitation program

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led to the need for a thorough understanding of the interaction between ultrasonic waves and biological matter. Scientific evidence of US therapeutic effectiveness in rehabilitation fields requires more attention on the technical specifications of devices used, and the exact parameters applied in the treatment of selected patients in order to avoid standardized US treatments using 'protocols' and non‐specific parameter settings.

