A shoulder specialist explains why you can still lift your arm with a rotator cuff tear. Other shoulder muscles compensate for the damaged ones, so normal motion doesn't rule out a tear.
Here's a myth I hear all the time as a shoulder specialist: I didn't think I had a rotator cuff tear because I can lift my arm. The reality is most people who have a rotator cuff tear still maintain function because you have remaining rotator cuffs intact and you have about 20 muscles that help drive the function of your shoulder. Being able to lift your arm doesn't mean that you don't have a rotator cuff tear.
