Anterior Glenohumeral Laxity Is Associated With Posterior Shoulder Tightness Among Professional Baseball Pitchers

Abstract

Background: Baseball pitchers often have increased anterior glenohumeral (GH) laxity and posterior shoulder tightness due to large forces produced during the throwing motion. As such, many clinicians have hypothesized that a relationship exists between these common characteristics. Hypothesis: A negative relationship will exist between anterior GH laxity and the summation of GH adduction range of motion (ROM) and GH internal rotation ROM asymmetry. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Anterior GH laxity, GH rotation ROM, and GH horizontal adduction ROM were measured in 58 asymptomatic professional baseball pitchers. Differences in GH internal rotation at 90° of abduction were calculated between both shoulders. A multiple regression analysis was used to determine the strength of the relationships between anterior GH laxity (dependent variable) and GH adduction ROM and GH internal rotation ROM asymmetry (independent variables) (P < .05). Results: A large portion of anterior GH laxity was predicted by the summation of GH adduction ROM and GH internal rotation ROM asymmetry (r2 = .45, P = .001). Furthermore, increased anterior GH laxity had a significant relationship with both decreased GH horizontal adduction ROM (r = .53, P = .001) and differences in GH internal rotation ROM (r = .43, P = .001). Conclusion: The results of this study suggest that decreased GH horizontal adduction and internal rotation ROM may be considered partial predictors for increased anterior GH laxity in the throwing arm of baseball players. Because of the association between these variables, clinicians may find it advantageous to address posterior shoulder tightness during the prevention, diagnosis, and treatment of shoulder injuries associated with anterior GH laxity.