Objectives:Glenohumeral internal rotation deficit (GIRD) indicates a 20 degree or greater loss of IR on the throwing shoulder compared to the non-throwing shoulder. The purpose of this study was to determine whether GIRD and/or bilateral difference in total rotational motion (TRM) of the glenohumeral joint (external rotation + internal rotation) correlated with shoulder injuries in professional baseball pitchers.Methods:This study was conducted over eight competitive seasons (2005-2012). Each year during spring training, the same examiners assessed passive range of motion (PROM) of both the dominant and non-dominant shoulders of professional pitchers using a bubble goniometer. In total, 505 examinations were conducted on 296 pitchers. Glenohumeral joint motion was assessed in supine with the arm at 90 degrees of abduction and in the plane of the scapula for ER and IR. During ER and IR ROM assessment, the scapula was stabilized per methods previously established. Shoulder injuries and days missed due to injury were assessed and recorded by the medical staff of the team.Results:Significant differences were noted during side-to-side comparisons (p<0.0001) within subjects. Amongst this cohort, there were 77 shoulder injuries in 52 players accounting for a total of 3131 days missed. GIRD did not correlate to increased risk of shoulder injuries (p=0.8629). Pitchers with a deficit of more than 5 degrees in TRM between shoulders had a 1.9x higher risk of injury (p=0.0290). Players with < 5 more degrees of ER motion in their dominant shoulder at 90 degrees of abduction were 2.2 times as likely to have a shoulder injury (p=0.0112).Conclusion:Based on these results, pitchers with bilateral differences in total rotational motion had a significant impact on the risk of shoulder injuries. Loss of ER PROM in the dominant shoulder compared to the non-dominant side appears to contribute to shoulder injury risk as well. Clinicians need to be aware of these findings and plan a program that addresses these issues.