July 2025

Updates on Glenohumeral Rotation Motion in the Baseball Athlete

Maintaining throwing arm total shoulder range of motion is imperative for baseball players.¹ Over the past two decades, total range of motion loss has been thought to be a result of glenohumeral internal rotation (GIR) differences between the throwing arm and non-throwing arm [commonly known as glenohumeral internal rotation deficit (GIRD)].²Researchers began investigating GIRD, linking its presence on the throwing arm to injury across different levels of baseball athletes.^3–5 However, the underlying mechanism(s) that explained why GIRD occurred was not accounted for during these risk factor studies. Efforts to investigate the contributing factors affecting GIRD led to the studying of humeral retrotorsion (HRT) in baseball athletes.⁶ It was determined that HRT helps to explain more than 50% of a player’s GIR.⁷ Consequently, it was suggested that glenohumeral motion should be interpreted within the context of HRT. In fact, when researchers account for HRT when measuring GIR (Figure 1) and glenohumeral external rotation (GER, Figure 2), GIRD is no longer present and deficits in GER become present.^8–10These findings certainly have clinical implications, as restrictions in GIR are likely not as prevalent as originally thought, and instead, GER restrictions are being observed.¹¹ Research supports measuring glenohumeral rotational motion within the context of HRT to determine if restrictions are coming from GIR or GER in baseball athletes.^1,8–11Musculoskeletal (MSK) ultrasound (US) is commonly used to measure HRT in the clinic (Figure 3); in instances where MSK US is not available, Bullock and colleagues¹ developed a model that can be used to predict a baseball athletes’ HRT (scan QR code to gain access to interactive document that predicts HRT).

*“Differentiation of Bony and Soft-Tissue Adaptations of the Shoulder in Professional Baseball Pitchers” Reuther et al, 2018. This study examined clinical versus HRT-corrected GIR and GER in healthy professional baseball pitchers. When HRT-correction was used on GIR motion, GIRD was not present. Further, GER deficits were present with HRT-correction. The findings provide evidence for the increasing shift away from using clinical total motion methods and the common assumption that baseball athletes often present with GIR loss and GER gain in the throwing shoulder. Accounting for HRT is important for clinicians to identify the effective treatment strategy and monitor progress.

*“Development and Internal Validation of a Humeral Torsion Prediction Model in Professional Baseball Pitchers” Bullock et al, 2021. Since many clinicians may not have access to MSK US to measure HRT, the authors developed a HRT prediction model as a valid alternative. The prediction model used statistical methods to calculate probability and found: 1) Every 3° increase in GIR explains a 1° increase in HRT, 2) Every 3° increase in GER explains a 1° decrease in HRT, 3) Every 7° increase in shoulder horizontal adduction explains a 1° increase in HRT, and 4) Right-handed baseball athletes had 2° less humeral torsion compared to left-handers. Clinicians can input a baseball athlete’s clinical measures of shoulder motion and quickly get bilateral HRT, and HRT-corrected GIR and GER using the HRT prediction calculator provided in the Resources section.

“The Role of Humeral Torsion on Glenohumeral Rotation in Injured Baseball Players” Entler et al, 2024. This is the first study to report clinical vs HRT-corrected GIR and GER disparities in baseball athletes with shoulder or elbow injuries. Applying HRT-correction, injured baseball athletes displayed GER deficits on the injured side compared to the non-injured side. Conversely, when HRT was not accounted for, GIRD was present. These results highlight the importance of measuring bony changes to decipher where the true motion loss is so baseball athletes with shoulder or elbow injuries receive appropriate care. Clinicians can learn more about how to assess and treat GER deficits by watching the Ask the Expert video provided in the Resources section.

*Not open-access, however abstracts are available

Ask the Expert: How to assess and treat GER loss

REFERENCES

1. Bullock GS, Shanley E, Collins GS, et al. Development and internal validation of a humeral torsion prediction model in professional baseball pitchers. J Shoulder Elbow Surg. 2021;30(12):2832-2838.

2. Rose MB, Noonan T. Glenohumeral internal rotation deficit in throwing athletes: current perspectives. Open Access J Sports Med. 2018;9:69-78.

3. Shanley E, Kissenberth MJ, Thigpen CA, et al. Preseason shoulder range of motion screening as a predictor of injury among youth and adolescent baseball pitchers. J Shoulder Elbow Surg. 2015;24(7):1005-1013.

4. Shanley E, Rauh MJ, Michener LA, Ellenbecker TS, Garrison JC, Thigpen CA. Shoulder range of motion measures as risk factors for shoulder and elbow injuries in high school softball and baseball players. Am J Sports Med. 2011;39(9):1997-2006.

5. Shitara H, Kobayashi T, Yamamoto A, et al. Prospective multifactorial analysis of preseason risk factors for shoulder and elbow injuries in high school baseball pitchers. Knee Surg Sports Traumatol Arthrosc. 2017;25(10):3303-3310.

6. Greenberg EM, Fernandez-Fernandez A, Lawrence JTR, McClure P. The development of humeral retrotorsion and its relationship to throwing sports. Sports Health. 2015;7(6):489-496.

7. Helmkamp JK, Bullock GS, Rao A, Shanley E, Thigpen C, Garrigues GE. The relationship between humeral torsion and arm injury in baseball players: A systematic review and meta-analysis. Sports Health. 2020;12(2):132-138.

8. Myers JB, Oyama S, Goerger BM, Rucinski TJ, Blackburn JT, Creighton RA. Influence of humeral torsion on interpretation of posterior shoulder tightness measures in overhead athletes. Clin J Sport Med. 2009;19(5):366-371.

9. Reuther KE, Sheridan S, Thomas SJ. Differentiation of bony and soft-tissue adaptations of the shoulder in professional baseball pitchers. J Shoulder Elbow Surg. 2018;27(8):1491-1496.

10. Entler K, Kruseman JK, Kennedy SM, et al. The role of humeral torsion on glenohumeral rotation in injured baseball players. Orthop J Sports Med. 2024;12(8):23259671241260084.

11. Paul RW, Sirch FR, Vata A, et al. Chronic adaptations of the shoulder in baseball pitchers: A systematic review. Am J Sports Med. Published online March 3, 2025:3635465251317202.

This content was developed in part by Natalie L. Myers, PhD, LAT, ATC, PES; Sean M. Kennedy, PT, DPT, PhD(c), SCS, CSCS; Kellie C. Huxel Bliven, PhD, ATC, FNAP; Alicia Lacy, PhD, ATC and the NATA Foundation Educational Resources Committee.

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