How can I tell if I have symptoms of rotator cuff injury?

See below. Symptoms vary with severity, but usually pain when you try to use the arm, particularly elevating the arm to reach out for something, difficulty lying on that side at night, pain radiates to the side of the upper arm. With a severe rotator cuff tear you may not be able to lift the arm above shoulder level due to a complete tear. Weakness of certain muscles called external rotator muscles as well.