Measurement Snapshot
ReferenceTraditional reference: 70 degrees
Common Adult RangeCommon adult active range: 60 to 75 degrees
Primary MusclesSubscapularis, teres major, latissimus dorsi, pectoralis major
Internal rotation is useful in overhead athlete and posterior capsule workflows, but side-to-side comparison and total arc context matter more than a single isolated value.
Standardized Setup
- Patient Position
- Place the patient supine with the shoulder abducted to 90 degrees, elbow flexed to 90 degrees, and forearm vertical at the start.
- Stabilization
- Apply scapular stabilization so the anterior shoulder does not lift away from the table as the forearm rotates downward.
- Landmarks
- Use the olecranon as the axis, a vertical line as the stationary reference, and the ulna toward the ulnar styloid as the moving reference.
Step-by-Step Protocol
- Set the shoulder and elbow at 90 degrees and calibrate the vertical forearm as zero.
- Rotate the forearm toward the table while keeping the scapula controlled.
- Stop at the first scapular lift, pain-limited end range, or true rotational limit.
- Document side, active or passive status, and whether the measured shoulder is dominant.
Common Measurement Errors
- Letting the scapula tip forward off the table.
- Changing the shoulder abduction angle during rotation.
- Mounting the phone obliquely instead of parallel to the ulna.
Cobb Angle Pro Workflow
- Choose Shoulder Internal Rotation and confirm the supine 90/90 setup.
- Mount the phone along the distal forearm or use a clinician-held overlay aligned to the ulna.
- Capture the endpoint before scapular compensation and save notes about dominance and sport demands.
References
- Wilk KE, Reinold MM, Dugas JR, et al. Glenohumeral internal rotation deficit in overhead athletes. Am J Sports Med. 2011;39(2):384-391.
- Kendall FP, McCreary EK, Provance PG, et al. Muscles: Testing and Function with Posture and Pain. 5th ed. Lippincott Williams & Wilkins; 2005.