Ultrasound uses high frequency sound waves to produce images of the body. An ultrasound scan is sometimes also called a sonograph.
When the sound waves are directed at your body, they are able to pass through liquid and soft tissues but not solid objects. When the ultrasound hits a dense or solid object, such as bone or tendons, it bounces back as an echo. Echoes of different strengths are reflected depending on the density of the object. These echoes are then translated by a computer into an image.
Ultrasound is painless and non-invasive. Because it uses sound waves, rather than radiation as in an X-ray, it is thought to be completely safe. Ultrasound is particularly good at providing images that would be harder to achieve with an X-ray such as the rotator cuff tendons. Ultrasound may also be used to guide diagnostic or therapeutic injection such as into the Acromioclavicular joint, calcific tendonitis or around tendons.
Ultrasound picture showing a tear of the supraspinatus tendon