I've seen two different orthopedic surgeons for a shoulder problem. One thinks I have tendinitis. The other thinks I have a rotator cuff tear. Both doctors did a bunch of tests. Is it really this hard to tell what's wrong?
Yes and no. Rotator cuff tears (RCTs) are easy to identify with arthroscopic exam. But this requires surgery and is invasive and expensive. Arthroscopic examination is 100 percent accurate.

Physical tests and imaging studies vary in specificity and sensitivity. Specificity refers to the ability of a test to determine a true negative response. Sensitivity shows the ability of a test to determine a true positive response. Sometimes a test has high specificity but low sensitivity or vice versa. The ideal test has high specificity and high sensitivity.

A simple X-ray isn't helpful in finding RCTs. Shoulder arthrography (injecting dye into the joint) is invasive and not always accurate. Ultrasound can be useful and is noninvasive but not always reliable. MRIs are the most sensitive and specific but very costly.

Researchers are doing studies using a handheld muscle testing device called a dynamometer to identify RCTs. A recent study from Australia showed this test has a 83 percent sensitivity and 79 percent specificity. The device is held against the patient's arm as he or she presses against it by using muscle contraction force. A torn tendon gives a weak muscle test.

If there aren't clear signs of a RCT you may be a good candidate for a rehab program. Most surgeons require at least six to eight weeks of conservative care for small RCTs. Time may be on your side -- with rehab and a little extra time, your symptoms will likely either improve or get worse. Sometimes the diagnosis of a RCT needs this kind of approach.