Shoulder Internal Rotation
Definition
The rotational movement of the humerus toward the midline with the arm at 90 degrees of abduction. Normal range is approximately 60-80 degrees. GIRD (Glenohumeral Internal Rotation Deficit) is a common finding in overhead athletes where one side has significantly less internal rotation than the other.
Clinical Significance
Shoulder internal rotation deficit is a strong predictor of shoulder injury in throwing and overhead athletes. The total arc of rotation (internal + external) should be approximately equal between sides. When internal rotation is lost, the posterior capsule is typically tight, and the shoulder compensates with scapular protraction or thoracic rotation. Internal rotation restriction also limits reaching behind the back, cross-body movements, and many activities of daily living.
How AKMI Assesses This
AKMI measures shoulder internal rotation bilaterally at 90 degrees abduction in supine position. The total arc of rotation (IR + ER) is calculated for each side and compared. Cross-referenced with scapular position and thoracic rotation to identify whether the restriction is glenohumeral or compensatory.
Get your shoulder assessed
A biomechanical assessment measures shoulder internal rotation and its relationship to the rest of your structural chain. 18 tests, objective data, personalized programming.