When I was pregnant I had an ultrasound of the baby and could see everything clearly. Yesterday I had an ultrasound of my shoulder for a torn rotator cuff tendon but I couldn't tell a thing. What can the doctor see with this test?

Even a doctor might not recognize the results of an ultrasound (US) of soft tissue structures without some training. Most have years of training and experience to accurately diagnose problems.

An ultrasound of the shoulder can show, first of all, if there is a torn tendon. It can show which tendon is damaged and if the tear is partial or through the full thickness of the tendon. Anyone trained to read US images can also tell the size of the tear and which direction it's going (up and down or sideways).

Sometimes with a full-thickness tear the tendon pulls away from the bone. This is called retraction. Small amounts of retraction are difficult to see with in an US image. Retraction more than one centimeter shows up more clearly.