Is there any way to tell if you have just hurt your shoulder by pulling it or twisting it, or if it is something more serious like a torn rotator cuff?

The only way to be sure that your injury is a rotator cuff injury is to have it diagnosed by your doctor. To do this, you may have x-rays, an ultrasound or an MRI (magnetic resonance imaging) that allows the doctor to see the soft tissue and any damage.

Another test, called an arthrogram may be done. This is also an x-ray, but dye is injected into the shoulder first so that the joint can be seen more clearly.