Influence of humeral torsion on interpretation of posterior shoulder tightness measures in overhead athletes
Myers JB, Oyama S, Goerger BM, Rucinski TJ, Blackburn JT, Creighton RA. Clin J Sport Med. 2009 Sep;19(5):366-71.

Decreased glenohumeral internal rotation is commonly seen in overhead athletes and may be caused by both soft tissue and bony adaptations (e.g., humeral torsion). However, clinically it is very difficult to differentiate between the amount of bony changes and soft tissue changes. Therefore, the authors examined humeral torsion and clinical measures of posterior shoulder tightness (glenohumeral internal rotation deficit [GIRD], horizontal adduction, total motion difference) and evaluated an adjustment of glenohumeral range of motion based on humeral torsion. This study measured humeral torsion and posterior shoulder tightness in 29 intercollegiate baseball players and 25 college-aged healthy participants. Humeral torsion was measured with a diagnostic ultrasound and a digital inclinometer. Glenohumeral range of motion, measured with a digital inclinometer, was reported with and without an adjustment for humeral torsion. The authors found that the dominant limb of baseball players had more humeral torsion, as well as less unadjusted internal rotation and total motion compared to the non-dominant arm and the control group. However, after adjusting for humeral torsion the between arm and group differences were no longer present. Significant relationships were observed between humeral torsion and several measures of posterior shoulder tightness.

The results of this study suggest that humeral torsion accounts for a majority of internal rotation loss and gain in external rotation. Humeral torsion has been previously demonstrated in overhead athletes, however glenohumeral range of motion has never been adjusted to identify the contribution of bone and soft tissue adaptations that are present. GIRD and horizontal adduction has been thought to be an indicator of posterior shoulder tightness, however the results of this study suggest that humeral torsion can have a significant effect on these clinical measurements. Burkhart ( suggested that a GIRD of greater than 20 degrees represents significant soft tissue adaptation, specifically of the posterior capsule. However, this population of baseball players had a GIRD of only 14 degrees. According to Burkhart this population may not have posterior capsule adaptations contributing to the loss of internal rotation, which agrees with the present results. It would be interesting to know if these baseball players were currently on a posterior shoulder stretching protocol to minimize any soft tissue changes. Clinically it is difficult to measure the amount of humeral torsion and identify players with soft tissue adaptations. How do you determine which players have a soft tissue adaptation that needs to be addressed with stretching? Do you stretch every baseball player or only players with a GIRD greater than 20 degrees?

Written by: Stephen Thomas
Reviewed by: Jeffrey Driban