Q: Everyone I see tells me I have a shoulder impingement problem yet I keep having to go for more tests. First it was X-rays, now it's an MRI. If they know what's wrong with me, why do I need another expensive test?

A:  A very good question. Let's start with the type of problem you have. The term impingement tells us something is getting pinched. But with so many different soft tissues around the shoulder, exactly what is getting pinched can vary from one person to another.

The most common shoulder impingement is referred to as subacromial impingement syndrome or SIS. This type of impingement occurs when the rotator cuff tendons rub against the roof of the shoulder, the acromion.

Although SIS is one term, it actually represents a wide range of underlying pathologies. There could be a bursitis, rotator cuff tendinopathy, fracture, calcific tendinitis, or other change in the local anatomy contributing to the problem. And before a plan of treatment can be determined, an accurate diagnosis is needed. That's where all these tests come in.

The physician usually begins with a detailed history of the problem and then conducts some clinical tests checking your movement and strength. None of the clinical tests available is 100 per cent accurate. By combining a few different clinical tests, the physician can get a better idea of what's going on.

MRIs add to that information and are usually recommended before doing surgery or other invasive procedures. The only truly accurate test is an arthroscopic examination but that is a surgical procedure and is saved for last when it looks like surgery may be needed anyway.

Reference: Marwan Alqunaee, RCSI, et al. Diagnostic Accuracy of Clinical Tests for Subacromial Impingement Syndrome: A Systematic Review and Meta-Analysis. In Archives of Physical Medicine and Rehabilitation. February 2012. Vol. 93. No. 2. Pp. 229-236.