The use of ultrasonic sound for diagnosis and treatment in human and equine medicine is not new, and in fact is becoming commonplace. Most horse breeders, for example, are familiar with the use of diagnostic ultrasound to detect and monitor reproductive problems and pregnancy. Sport horse owners in large numbers have seen ultrasound employed in diagnosing ligament and tendon injuries. But perhaps not quite so common is the use of ultrasound to facilitate recovery from injury. It is an intriguing and beneficial modality for treating a variety of problems in equines, particularly in the limbs.

Therapeutic ultrasound is capable of significantly raising the temperature of deep tissues. This provides for much greater therapeutic potential than, for example, merely applying external heat to a limb. When heat is applied, the skin becomes very warm, but often the deep tissues–where heat is needed–are not affected by surface warming.

Ultrasound is capable of heating these deep tissues without elevating the temperature at the skin surface, says Mimi Porter, an equine physical therapist from Lexington, Ky., who is the author of Equine Sports
Therapy
, a book that delves into a variety of therapeutic modalities.

Because of its penetrating nature, ultrasound can be used to selectively heat certain tissues, such as muscles and ligaments, while avoiding excessive heating of the overlying skin.

As pointed out in an earlier article on basic physical therapy (The Horse of May 1997, page 59), heat can be beneficial in the healing process.

Porter explains it this way: “Heating, being a form of energy, increases metabolic activity in the cells. This increased activity causes an increase in oxygen demand locally. As a result, vasodilation occurs to increase the amount of blood bringing oxygen and nutrients to the area. Membrane diffusion and enzymatic activity also increase, enabling oxygen consumption