I tore my rotator cuff playing tennis. During an overhead serve, I felt a painful pop. Afterwards, I couldn’t lift my arm. The doctor told me I tore the biceps tendon and the subscapularis tendon. How could my doctor tell exactly which muscles were torn?

There are many specific tests doctors can use to test each muscle of the shoulder. Each muscle attaches to the bone by its tendon. Just palpating or pressing on each tendon will give some information. The patient’s report of how the injury occurred and what the symptoms were at the time of the injury also help.

How the shoulder moves and when pain occurs adds another piece of information. For example, if a specific shoulder motion is painful but strong, a minor tear is suspected. A painful and weak response suggests a partial tear of the muscle or tendon. A completely torn muscle/tendon is painless and weak.

The biceps muscle has two parts: the long head and the short head. With complete rupture of the long head of the biceps, the patient has no pain and there is a bulging of the muscle.

Imaging studies such as X-rays and MRIs also offer useful information in making the diagnosis. The final diagnosis is made (or confirmed) when the doctor uses an arthroscope to look inside the joint. Partial or complete tears can be seen during this test.