Camp CL, Zajac JM, Pearson DB, et al. Decreased shoulder external rotation and flexion are greater predictors of injury than internal rotation deficits: Analysis of 132 pitcher-seasons in professional baseball. Arthrosc J Arthrosc Relat Surg. 2018;33(9):1629-1636. doi:10.1016/j.arthro.2017.03.025.
Glenohumeral (GH) internal rotation deficit (GIRD) has been defined as a > 20-degree deficit in GH internal rotation (IR) in the throwing shoulder compared with the non-throwing shoulder. The presence of GIRD has been implicated as a cause of both shoulder and elbow injuries in baseball players1-3. Wilk et al.1 found GIRD and a 5-degree loss of total range of motion (TROM) was correlated with a shoulder injury in professional baseball players over a single season. Later work by Wilk et al.2 found GIRD, TROM, and flexion deficit was not significantly related to shoulder injury in these same players tracked over five years. However, Wilk et al.2 did show decreased shoulder external rotation (ER) range of motion (ROM) was correlated with a shoulder injury when these players were tracked over five years. In the same sample, Wilk et al.3 found TROM deficit and GH flexion deficit increased the risk of an elbow injury but GIRD and ER deficits did not.
The purpose of this study was to (1) describe normal ROM for elite-level pitchers, (2) describe the characteristics of shoulder and elbow injuries in professional pitchers over a 6-year period in one MLB organization, and (3) to identify ROM deficits that were independently associated with a future shoulder or elbow injury.
Study Population & Methods
Over the course of five MLB spring training camps for one team, all pitchers underwent a comprehensive physical examination. Inclusion criteria included a willingness to participate in the assessment, absence of any injury or recent surgery that precluded full examination, and the ability to fully participate in all baseball-related activities. Players were excluded if they were unable to fully participate in baseball activities, had a prior injury for which they had not fully recovered, or were unwilling to participate in the physical examination.
Pitchers were prospectively followed over the course of the season and all subsequent injuries were recorded and cataloged. Injuries occurring by traumatic mechanisms were excluded. ROM assessment included the following passive movements: GH IR, GH ER, GH flexion, GH horizontal adduction, elbow flexion, and elbow extension. A total of 136 pitcher seasons of ROM were initially identified but 4 were excluded for incomplete injury recovery (n=132).
- No categorical variables significantly increased the risk of shoulder injury alone.
- The presence of a shoulder flexion 5-degree deficit showed an OR of 2.83 (95% CI 1.04-7.73; P = .042) for an elbow injury.
- GIRD was not associated with an increased risk of injury to the shoulder or elbow.
- For continuous variables, the most significant risk factor for shoulder or elbow injury was increasing ER deficit (OR 1.08; 95% CI 1.02-1.14; P = .015).
- The risk of elbow injury increased by 7% for each degree of increased shoulder ER deficit (OR 1.07; P = .030) and 9% for each degree of decreased shoulder flexion (OR 1.09; P = .017).
- Reliability of ROM measurements was not investigated.
- Shoulder flexion was not measured during the first year of the investigation.
- Pitching workload was not investigated or controlled for in the study.
- Only one professional organization’s players were investigated.
- Study design shows correlations but cause and effect inferences cannot be made.
Practical Implications & Closing Thoughts
This study showed preseason shoulder ER and flexion ROM deficits are independent risk factors for elbow injuries during a professional baseball season. The correlation of shoulder flexion and ER deficits with elbow injury in this study is similar to those reported in previous research2,3. These ROM deficits were shown to be more closely correlated with injuries than GIRD and TROM deficits. A recent meta-analysis by Keller et al. also showed ROM deficits, including GIRD, were not a significant risk factor for shoulder and elbow injury in baseball pitchers.
This study found the dominant shoulder demonstrated decreased GH IR (mean 13.2 degrees), GH flexion (mean 4.1 degrees), horizontal adduction (mean 4.5 degrees), and GH TROM ( mean 4.7 degrees), whereas GH ER was increased (mean 7.8 degrees) compared with the opposite side. Therefore, it may be plausible to target near symmetrical TROM, flexion, and horizontal adduction ROM in baseball pitchers. TROM with greater relative ER and less IR compared to the non-throwing shoulder may be most desirable. Future research is needed to elucidate the optimal contributions of ER and IR to TROM in the overhead athlete.
Restricted shoulder ER and flexion did not impact injury risk to the shoulder itself, but they had a significant effect on the elbow. This highlights the importance of the kinetic chain in generating, transferring, and dissipating forces during baseball pitching. Inadequate shoulder flexion and ER may disrupt the kinetic chain’s ability to do so. Manual therapy and mobility exercises targeting the latissimus dorsi, teres major, pectoralis minor and major, and the rotator cuff should be considered as components of an in-season and off-season arm care program.
- Wilk KE, Macrina LC, Fleisig GS, et al. Correlation of glenohumeral internal rotation deficit and total rotational motion to shoulder injuries in professional baseball pitchers. Am J Sports Med. 2011;39(2):329-335. doi:10.1177/0363546510384223.
- Wilk KE, Macrina LC, Fleisig GS, et al. Deficits in glenohumeral passive range of motion increase risk of shoulder injury in professional baseball pitchers. Am J Sports Med. 2015;43(10):2379-2385. doi:10.1177/0363546515594380.
- Wilk KE, Macrina LC, Fleisig GS, et al. Deficits in glenohumeral passive range of motion increase risk of elbow injury in professional baseball pitchers: A prospective study. Am J Sports Med. 2014;42(9):2075-2081. doi:10.1177/0363546514538391.
- Keller RA, De Giacomo AF, Neumann JA, Limpisvasti O, Tibone JE. Glenohumeral internal rotation deficit and risk of upper extremity injury in overhead athletes: A meta-analysis and systematic review. Sport Heal A Multidiscip Approach. 2018;Online:1-8. doi:10.1177/1941738118756577.