How Does Ultrasound Therapy Work?

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The sonar used in submarines and other naval vessels prior to WWII had a devastating impact on marine life. When marine biologists studied the remains of fish and other aquatic creatures killed by the sound waves, they found that the deaths resulted in overheating of tissues. That discovery instigated research into the possible therapeutic effects that sound waves might have on the human body and ultrasound technology became a reality.

About Ultrasound Technology

Today, the technology involves applying the waves using a probe or a wand having a rounded or knobbed end that comes in direct contact with a patient's skin. Prior to therapy, a technician applies a special topical gel, which not only reduces skin friction but also enhances sound wave transmission. The waves are transmitted at frequencies ranging between 0.8 and 3.0 MHz. The lower the frequency, the greater the depth at which the waves effectively penetrate.

The waves are created using a piezoelectric effect, whereby electric current causes vibrations of the crystals contained within the wand. The waves penetrate the skin and in turn vibrate contacted tissues. The vibration generates heat within the affected area. However, the sensation is not generally felt by the patient. When heated treatments are ill-advised, therapists use pulsed rather than continuous ultrasound transmissions.

Ultrasound Effects

In addition to creating heated tissues, ultrasound waves relax tissues, deteriorate scar tissues and improve local blood and lymph circulation. Enhanced circulation speeds the healing process while reducing inflammation and swelling. By altering the intensity or the power density of the sound waves, therapists achieve the desired effects. Ultrasound can also be used to administer phonophoresis, which is a non-invasive means of delivering medications. Steroids or other formulations are applied topically. The ultrasound waves then transport the medication deep into the tissues.

Ultrasound Treatments

Ultrasound therapy sessions typically last anywhere from three to five minutes. However, the duration of each session depends on the type of condition requiring treatment and the size of the area being treated. In the case of adhesion or scar tissue breakdown, therapy sessions last longer. During the course of the session, the technician keeps the wand or probe in constant motion, which prevents unnecessary energy build-up over one location and subsequent discomfort.

Some of the many conditions effectively treated using ultrasound include muscle spasms, tendinitis, and minor joint swelling. The sound waves generated by the technology can also pinpoint fractures as the waves become trapped within the bone cell spaces and build. The excess energy then causes a sharp pain at the area of the break.


Ultrasound should never be administered over infections, known malignancies or metal implants. Abdominal treatment is also not advised in pregnant women. Other restricted areas include bone growth plates in children, the spinal column following laminectomies, over the head or reproductive regions.

Cite this page: N., Sam M.S., "How Does Ultrasound Therapy Work?," in, March 25, 2016, (accessed October 4, 2022).