Ultrasound (US) is a modality used by physiotherapists to increase the rate of tissue healing, to treat chronic inflammation and other fibrotic conditions, and for pain management. US treatment should not cause pain. It can be thermal, which means the tissues will be heated, or athermal, meaning no heat will be applied to the tissues.

US machines send sound waves through the tissues and causes molecules in the tissues to oscillate in the area of treatment. When on a thermal setting, this will cause heating of the tissues; an athermal setting is pulsed, the machine is only on a certain percentage of the time. This will increase the activity of the cells without heating them, which will help in tissue healing.

Thermal US is usually for chronic conditions and pain management. Athermal US is usually for tissue healing. Some of the conditions treated with thermal US include: complex regional pain syndrome, chronic inflammation, adhesions, tendonitis, and contractures. With thermal US treatment, you should only feel slight heating of the tissues and the sound head moving over the area of injury. Conditions treated with athermal ultrasound include: sprains, strains, overuse injuries, trauma, and surgical scars. With athermal US treatment, you should only feel the sound head moving over the tissues.