Sometimes the UCL (ulnar collateral ligament) is partially torn. This usually happens gradually from the high stress on the ligament that damages it little by little. This is similar to a rope being frayed or a rubber band being over-stretched again and again. Eventually it gets damaged too much to do its job and the elbow hurts during cocking and acceleration. This is less dramatic than when the ligament tears all at once, but can be just as painful. The ligament becomes stretched. The end result is that the elbow hurts too much to throw. Sometimes these partial tears can heal enough to allow the return to competition, but often the problem recurs again and again. In fact, in 2003 Dr. Sean Jereb and I did a study evaluating all athletes drafted by Major League Baseball Teams over a four-year period. In this study, we found that those athletes who had had a partial tear or “sprain” of their UCL while in amateur baseball had a very high recurrence rate and often had their careers cut short by their elbow injuries. So, when a thrower has repeated episodes of pain on the inner side of the elbow coming from a partially torn or stretched UCL a reconstruction may be necessary.
It is important to note that playing different positions places different stresses on the elbow. For example, catching is harder on the elbow than playing first base due to the repeated throws and the long throws to second base. Clearly, third base is more strenuous than playing second. Pitcher is the most strenuous of all. The number of high velocity throws, throwing breaking pitches, plus the extra momentum from throwing “downhill” off the mound increase the stress on the UCL. Many pitchers feel fine throwing on flat ground but have pain when throwing off the mound. This can be a source of great frustration when the pitcher is trying to rehab after an injury and is doing fine on his flat ground program but suddenly develops recurrent pain when returning to the mound. We always monitor our professional pitchers very closely at this stage because the transition from flat ground to the mound can sometimes be too much for the ligament to tolerate.