Ultrasound (US) treatment involves use of sound waves over the area being treated to create vibrations that generate heat. When the tissues vibrate, friction is produced at the molecular level, which causes the temperature of the tissues to increase. While heating packs can be effective in warming an affected area, they are unable to reach the depth that US can. It can also be used with an anti-inflammatory topical medication delivered directly to a specific area, in a process called phonophoresis..