Therapeutic ultrasound is the use of high frequencies of sound for therapeutic purposes. In physiotherapy applications, the frequency level is usually in between 0.7 to 3.3 MHz.
Maximum energy absorption is in between 2 to 5 cm below the skin. Ultrasound is absorbed primarily by connective tissue such as ligaments, tendons, fascia, scar tissues as well as muscle and fat tissue.
Therapeutic ultrasound may have two types of benefit: Thermal and non-thermal effects.
Thermal effects are due to increased molecular activity in tissue cells caused by the vibration of sound waves. This increase in temperature can be up to 5 degrees in superficial muscles with an application of 10 minutes of ultrasound.
Non-thermal effects of ultrasound are cavitation, microstreaming and acoustic streaming. Cavitational effects result from the vibration of the tissues which may lead to microscopic air bubble formation. It is also believed that vibrations caused by therapeutic ultrasound applications stimulate cell membranes. This physical stimulation is regarded to improve the cell-repair effects of the inflammatory conditions.
Although the effect of ultrasound is still being studied, the results of some studies confirm that ultrasound therapy may accelerate the healing process in damaged tissues. And therapeutic ultrasound is recommended for muscle, tendon, joint pain, as well as neuropathy and carpal tunnel syndrome.