“Unfortunately — although there are some interesting exceptions and tantalizing hopes for some conditions — ultrasound is not a promising therapy for most of the painful problems it is used for. There is a jarring, bizarre lack of quality research for such a popular, mainstream therapy. What little research is available paints a bland picture. Ultrasound therapy isn’t even on good theoretical foundations. At best, it’s more complicated and unpredictable than most therapists believe. At worst, there is no rational basis for US at all.”
“Ultrasound has been used as a treatment modality for sports injuries by therapists over the last 50 years.How does ultrasound work?Ultrasonic waves or sound waves of a high frequency that is not audible to the human ear are produced by means of mechanical vibration in the metal treatment head of the ultrasound machine. The treatment head is then moved over the surface of the skin in the region of the injury transmitting the energy into the tissues.
When sound waves come into contact with air it causes a dissipation of the waves, and so a special ultrasound gel is placed on the skin to ensure maximal contact between the treatment head and the surface of the skin and to provide a medium through with the sound waves can travel. Ultrasound can also be applied under water which is also a medium for ultrasound waves to travel through.”
Source: Ultrasound Therapy