Ultrasound is a modality that uses a transducer or an applicator head to transmit ultrasonic waves through a conducting gel into soft tissue. Therapeutic ultrasound has a penetration depth of 2 or 5 cm, depending on the amplitude of the wave. The ultrasonic waves are primarily absorbed by the muscles, tendons, ligaments, periosteum and fascia.
Therapeutic ultrasound has two mechanism of tissue healing, which are thermal and non- thermal. Thermal effects are due to the absorption of the sound waves which vibrates the tissue causing heat. Non-thermal effects of ultrasound are due to cavitation. Cavitation caused by therapeutic ultrasound occurs when the tissue vibrates, causing the formation of microscopic air bubbles. These air bubbles are thought to transmit vibrations in a way that stimulate cell membranes, enhancing the cell-repair effects of the inflammatory response.
The two mechanism of therapeutic ultrasound are thought to produce three primary benefits. The first benefit is that it increasing blood flow to the area being treated which speeds up the healing process. The second benefit is that it reduces swelling and edema, decreasing pain. Finally, therapeutic ultrasound is thought to gently massage muscle, tendons and ligaments, as no strain is added to the treatment