Ultrasound therapy is used by physios to treat a variety of conditions. The “ultra-“ refers to the frequency of the sound waves which is above the range of human hearing. Ultrasonic waves are produced by the ultrasound machine and transmitted to the body by the transducer, or treatment head which is moved over the injured area. When the waves come into contact with air, they dissipate and so a gel is applied to the skin to ensure maximum transmission of the ultrasound waves to the injured area.

Ultrasound has several effects on the body which make it useful in the treatment of injuries:

  • Accelerated healing
  • Analgesia (reduction in pain)
  • Assists in decreasing muscle spasm
  • Stimulation of fracture healing

These are due to the following effects of ultrasound:


The ultrasound waves cause the tissues in the body to alternately compress and expand which results in small changes to the shape of the cells. This is useful when trying to reduce swelling.


The ultrasound waves cause the tissues to heat up. This has several useful effects:

  • Increased blood flow to the area. Blood brings oxygen which is needed for healing and removes waste products caused by injury.
  • Increased metabolism (the chemical processes happening within the cells). More energy means faster healing.
  • Stimulates collagen production. Collagen is one of the building blocks of muscles, tendons and ligaments.
  • Increased extensibility of connective tissue, e.g. ligaments and tendons – it makes them more stretchy. This is useful when treating older injuries where there is already scar tissue.