Ultrasound Therapy is one of the most commonly used and well accepted electrotherapy modality in treating various musculoskeletal conditions. Ultrasound therapy is usually used with the help of a coupling media. The coupling media, such as water, oil or gel prevents reflection of the ultrasonic wave away.

The two main types of ultrasound therapy are thermal and mechanical. Both use sound waves generated by a transducer head (which looks a bit like a microphone) to penetrate soft tissues.

The most common frequencies used for medical purposes range from 0.8 MHz to 3 MHz. Most therapeutic US machines are set with frequencies of 1 MHz and 3 MHz. A lower frequency pushes sound waves to a greater depth in tissue, but the waves are less focused. Three MHz affects more superficial structures because of the attenuation of energy as it passes through the tissue. Attenuation is defined as the decrease in the energy of US as the distance it travels through increases. Clinically, a frequency of 1 MHz is reported to be most beneficial for reaching tissues at 2.5-5 cm and is recommended for deeper tissue or on patients with more subcutaneous fat. Whereas a frequency of 3 MHz is recommended for more superficial tissue at depths up to 2.5 cm. Three MHz heats up tissue three times faster than 1MHz, therefore the treatment time should be a shorter duration than a 1 MHz treatment. It has been reported that a frequency of 3 MHz is used most often because most of the tissue that the clinicians are trying to heat are more superficial.