Posterior shoulder capsules are thicker and stiffer in healthy college baseball players: A quantitative assessment using shear-wave ultrasound elastography.
Takenage T, Sugimoto KS, Goto H, Nozaki M, Fukuyoshi M, Tsuchiya A, Murase A, Ono T and Otsuka T. Am J Sports Med. 2015. [Epub Ahead of Print].
Take Home Message: Thickening of the posterior glenohumeral joint capsule is correlated with lower ranges of glenohumeral internal rotation in collegiate baseball athletes.
The glenohumeral joint experiences significant distraction forces (1.5 times body weight) during the deceleration phase of overhead throwing. Current research suggests that the posterior shoulder capsule thickens to accommodate this stress. However, the relationship between capsule thickness and its effect on glenohumeral internal rotation has not been conclusive. Therefore, Takenaga and colleagues completed a cross-sectional study to assess the thickness and elasticity of the posterior and posteroinferior capsule of the shoulder and its relationship to glenohumeral internal rotation in collegiate baseball players. The authors recruited 45 collegiate baseball players (male, ~20 years old, 13 pitchers) with no history of shoulder injuries. The authors evaluated posterior capsule thickness using shear-wave ultrasound elastography in both a seated position with the arm 0º abduction and adduction and 90º of shoulder flexion. Passive glenohumeral range of motion was assessed with a goniometer while the participant laid supine with the shoulder at 90º of abduction. Overall, both posterior and posteroinferior capsule stiffness and thickness in the throwing shoulder was greater than the non-throwing shoulder. Both capsule thickness and elasticity were negatively correlated with glenohumeral internal rotation. Hence, thicker capsules and greater stiffness were related with less glenohumeral internal rotation.
Overall, the authors presented interesting findings for clinicians, especially those dealing with overhead throwing athletes. The conclusions of the current study are in agreement with those of Thomas and colleagues, which suggest that the repetitive loading of overhead throwing may be a factor in the thickening of the posterior and posteroinferior joint capsule. This change is most likely a compensation to attempt to accommodate the large loads, however to absorb these large loads, range of motion will logically be limited. This would explain the second main finding that the increase in thickness would be negatively correlated with glenohumeral internal rotation. If clinicians do encounter patients with severely limited range of motion, they should seek to treat the posterior capsule tightness. To avoid excessive stretching proper assessments should precede this treatment strategy.
Questions for Discussion: What treatments have you found to be effective in treating limited range of motion in the shoulder of an overhead throwing athletes? Does this treatment effect the joint capsule to restore motion?
Written by: Kyle Harris
Reviewed by: Stephen Thomas