I went to a university orthopedic clinic for a shoulder exam. They found a rotator cuff tear. Now they want to inject a dye into the joint and take some pictures. Can't I just have a regular MRI and find out what they need without the injection?

MRIs (magnetic resonance imaging) give good information about the shoulder, which is a very complex joint. However it's not accurate 100 per cent of the time. In fact it may be only about 86 to 90 percent accurate.

The magnetic resonance arthrography (MRA) is more sensitive and more reliable for rotator cuff tears. It has been shown to be 100 percent accurate in some studies. The MRA is more expensive, takes a little longer, and does require a needle injection into the shoulder.

Most patients report it doesn't hurt as much as they expected. The MRA doesn't offer any advantage in diagnosis if there's damage outside the joint capsule. It does give the surgeon more information about the type, direction, and size of rotator cuff tears.