This descriptive anatomic study measured glenohumeral rotation and humeral retroversion in 54 asymptomatic college baseball players. It asked whether the classic external rotation gain and internal rotation loss in the throwing arm are explained by bony retroversion rather than soft tissue change.
When you measure a glenohumeral internal rotation deficit in a thrower, do not assume it is all posterior capsular tightness that stretching will fix. This paper shows the ER gain and IR loss track increased humeral retroversion, a fixed bony adaptation. Some of that motion asymmetry is uncorrectable.
The key mental model: total rotational motion is what matters clinically. If the arc is preserved and simply rotated toward ER, the shoulder is adapted, not pathologic. A true GIRD that outpaces the ER gain (loss of total arc) points to soft tissue tightness worth treating.
The retroversion likely develops from throwing loads on the open proximal humeral physis during growth. This is why bony adaptation is greatest in athletes who throw heavily as children.
Retroversion also cuts both ways in impingement. Increased retroversion may protect against posterosuperior glenoid impingement by allowing ER without capsular laxity, while decreased retroversion has been treated with derotational osteotomy.
This descriptive anatomic study measured glenohumeral rotation and humeral retroversion in 54 asymptomatic college baseball players. It asked whether the classic external rotation gain and internal rotation loss in the throwing arm are explained by bony retroversion rather than soft tissue change.
When you measure a glenohumeral internal rotation deficit in a thrower, do not assume it is all posterior capsular tightness that stretching will fix. This paper shows the ER gain and IR loss track increased humeral retroversion, a fixed bony adaptation. Some of that motion asymmetry is uncorrectable.
The key mental model: total rotational motion is what matters clinically. If the arc is preserved and simply rotated toward ER, the shoulder is adapted, not pathologic. A true GIRD that outpaces the ER gain (loss of total arc) points to soft tissue tightness worth treating.
The retroversion likely develops from throwing loads on the open proximal humeral physis during growth. This is why bony adaptation is greatest in athletes who throw heavily as children.
Retroversion also cuts both ways in impingement. Increased retroversion may protect against posterosuperior glenoid impingement by allowing ER without capsular laxity, while decreased retroversion has been treated with derotational osteotomy.