Therapeutic ultrasound

Therapeutic ultrasound is a technique that uses high-frequency sound waves (ultrasound) to speed healing in injured joint or muscle tissue. The frequency used is typically 1-3 Mhz. At this frequency, the waves tend to travel through tissue with high water or low protein content, and to bounce off cartilage and bone. They are absorbed primarily by connective tissue: ligaments, tendons, and fascia (and also by scar tissue).

Therapeutic ultrasound may have two types of benefit: Thermal effects involve energy absorbed from the sound waves heating the tissue. If the tissue is heated to 40-45C (104-113F), it can enter a state of hyperaemia (increased blood flow), which speeds healing and reduces chronic inflammation. Cavitational effects result from the vibration of the tissue causing microscopic air bubbles to form, which transmit the vibrations in a way that directly stimulates cell membranes. This physical stimulation appears to enhance the cell-repair effects of the inflammatory response.

Therapeutic ultrasound is sometimes recommended for muscle as well as joint pain, although some evidence suggests it may not be effective for this purpose.