I did a little more research into the SLAP tear (what was being tested for today), otherwise known as a frayed or torn labrum (tendon deep in the shoulder). How's this for a quote (found in Slate Magazine, a subsidiary of NPR).

The leading minds in baseball medicine are flummoxed by the labrum. Doctors can't agree on how to detect a tear, don't know the best way to fix one, and aren't sure why, almost without fail, a torn labrum will destroy a pitcher's career... if pitchers with torn labrums were horses, they'd be destroyed. Of the 36 major-league hurlers diagnosed with labrum tears in the last five years, only (one) has returned to his previous level.

Darn it.