Shoulder and elbow injuries are on the rise among youth and professional baseball players.  Our previous post on baseball injuries detailed the risk of future injury if an athlete has lost range of motion in his shoulder prior to the season.  In particular, emphasis has been placed on the amount of internal rotation (hand behind lower back) in an athlete’s throwing shoulder.  A common adaptation in a thrower’s shoulder is to develop additional external rotation (cocking phase of throwing) and lose internal rotation (Figure A).  An important point is the athlete should maintain the same total range of motion from side to side given this adaptation (Figure B).  An at risk shoulder would have an total range of motion less than the uninvolved side.  

A recent prospective study in the American Journal of Sports Medicine examined the impact of a Professional thrower’s range of motion on their injury incidence during the season.  Wilk et al. examined 296 professional pitchers for range of motion and followed these players through the upcoming season.  As expected, the authors noted significant side to side differences in their shoulder range of motion.  51 pitchers reported 75 shoulder injuries for a total of 5570 days on the disabled list and 20 surgeries were performed.  The authors found <5 degrees greater external range of motion in the throwing shoulder of pitchers made them 2 and 4 times as likely to become placed on the disabled list or undergo surgery during the season.  

A thrower requires a greater degree of shoulder external rotation than another athlete, if this adaptation is not present it may be a sign of further problems.  In particular, the total range of motion should be measured and be equal between the throwing and non throwing shoulders.  For more injury prevention information or to address risk factors for your sport contact the experts and Mend Physical Therapy.