What is a torn rotator cuff tendon like?

Painful and weak. A torn rotator cuff tendon is usually quite painful, especially at night or during forceful shoulder motion. The rotator cuff starts out as 4 individual muscle attached to the shoulder blade. As they approach there insertion onto the tuberosities of the humerus, they come together to make a tendonus cuff. When this cuff of tissue is torn, active shoulder motion becomes difficult. Needs surgery.
Rotator cuff tear. Most common complaints associated with a rotator cuff tendon tear include pain in the upper arm, increases with lifting or reaching, pain at night, and sometimes weakness with lifting.
Weakness, pain. You have weakness when trying to raise your arm over your head, associated with pain. Typically rotating your arm in or out (such as with putting on a shirt) is also painful. An MRI of your shoulder can diagnose it best.