This case-control study asks what distinguishes the throwing shoulder that develops pathologic internal impingement from the healthy adapted thrower. Eleven baseball players with MR arthrogram-confirmed internal impingement were compared to 11 position-matched controls. It measures GIRD, external rotation gain, and posterior shoulder tightness to identify who is at risk.
When a baseball pitcher presents with posterior shoulder pain in late cocking, measure both shoulders. The teaching point of this paper is the distinction between normal adaptation and pathology.
Every thrower loses internal rotation, but the healthy shoulder compensates with an equal external rotation gain, preserving the ~180° total arc. Here, the impinged throwers lost internal rotation (19.7°) WITHOUT gaining external rotation, converting a benign adaptation into a true deficit.
The mental model: excessive GIRD plus posterior tightness shifts the glenohumeral fulcrum posterosuperiorly, driving the cuff undersurface against the posterior labrum and producing the SLAP and partial cuff lesions seen at arthroscopy.
Because posterior tightness is the modifiable culprit, first-line management is posteroinferior capsular stretching (sleeper and cross-body stretches), with roughly 90% of symptomatic throwers responding nonoperatively. Appraise this as Level 3 evidence with only 11 subjects and no control for humeral retroversion, so it establishes association, not causation.
This case-control study asks what distinguishes the throwing shoulder that develops pathologic internal impingement from the healthy adapted thrower. Eleven baseball players with MR arthrogram-confirmed internal impingement were compared to 11 position-matched controls. It measures GIRD, external rotation gain, and posterior shoulder tightness to identify who is at risk.
When a baseball pitcher presents with posterior shoulder pain in late cocking, measure both shoulders. The teaching point of this paper is the distinction between normal adaptation and pathology.
Every thrower loses internal rotation, but the healthy shoulder compensates with an equal external rotation gain, preserving the ~180° total arc. Here, the impinged throwers lost internal rotation (19.7°) WITHOUT gaining external rotation, converting a benign adaptation into a true deficit.
The mental model: excessive GIRD plus posterior tightness shifts the glenohumeral fulcrum posterosuperiorly, driving the cuff undersurface against the posterior labrum and producing the SLAP and partial cuff lesions seen at arthroscopy.
Because posterior tightness is the modifiable culprit, first-line management is posteroinferior capsular stretching (sleeper and cross-body stretches), with roughly 90% of symptomatic throwers responding nonoperatively. Appraise this as Level 3 evidence with only 11 subjects and no control for humeral retroversion, so it establishes association, not causation.