Cross-sectional CT study of 25 professional pitchers and 25 matched non-throwers. Measures bilateral humeral head retroversion, glenoid version, glenohumeral range of motion, and laxity. Asks whether the classic throwing-shoulder ER gain / IR loss paradox is driven by osseous or soft-tissue changes.
The textbook explanation for pitcher GIRD was a stretched anterior capsule and a contracted posterior capsule — a soft-tissue model that logically led to aggressive posterior capsule mobilization as first-line treatment.
This paper replaced that model. The ER/IR shift is osseous: increased humeral retroversion repositions the entire arc externally while total arc stays constant at ~189°. Laxity is symmetric, so the capsule is not the culprit.
When you see a pitcher with GIRD, calculate the total arc (ER + IR at 90°) bilaterally before intervening. If the bilateral total arc is symmetric (within ~5°), the shoulder has adapted normally. Stretching posterior contractile (muscular) tissue remains appropriate, but posterior joint mobilization misidentifies the pathoanatomy and is not supported by this data.
One timing nuance worth knowing: the adaptation is developmental and requires early loading during skeletal growth. A window of opportunity exists before physeal closure. All 25 pitchers in this study began throwing before age 10.
Cross-sectional CT study of 25 professional pitchers and 25 matched non-throwers. Measures bilateral humeral head retroversion, glenoid version, glenohumeral range of motion, and laxity. Asks whether the classic throwing-shoulder ER gain / IR loss paradox is driven by osseous or soft-tissue changes.
The textbook explanation for pitcher GIRD was a stretched anterior capsule and a contracted posterior capsule — a soft-tissue model that logically led to aggressive posterior capsule mobilization as first-line treatment.
This paper replaced that model. The ER/IR shift is osseous: increased humeral retroversion repositions the entire arc externally while total arc stays constant at ~189°. Laxity is symmetric, so the capsule is not the culprit.
When you see a pitcher with GIRD, calculate the total arc (ER + IR at 90°) bilaterally before intervening. If the bilateral total arc is symmetric (within ~5°), the shoulder has adapted normally. Stretching posterior contractile (muscular) tissue remains appropriate, but posterior joint mobilization misidentifies the pathoanatomy and is not supported by this data.
One timing nuance worth knowing: the adaptation is developmental and requires early loading during skeletal growth. A window of opportunity exists before physeal closure. All 25 pitchers in this study began throwing before age 10.