Measurement Snapshot
ReferenceTraditional reference: 90 degrees
Common Adult RangeCommon adult active range: 80 to 95 degrees
Primary MusclesInfraspinatus, teres minor, posterior deltoid
External rotation helps document rotator cuff and shoulder mobility workflows, especially when paired with internal rotation and total rotational arc.
Standardized Setup
- Patient Position
- Place the patient supine with shoulder abduction at 90 degrees, elbow flexion at 90 degrees, and the forearm vertical before rotation begins.
- Stabilization
- Stabilize the distal humerus and trunk to prevent spinal extension, elbow drift, or shoulder translation at end range.
- Landmarks
- Use the olecranon as the axis, vertical as the stationary reference, and the ulna toward the ulnar styloid as the moving reference.
Step-by-Step Protocol
- Calibrate the vertical forearm start position as zero.
- Rotate the forearm backward toward the table while maintaining shoulder and elbow position.
- Stop before spinal arching, shoulder translation, or elbow extension changes the test.
- Record active and passive values separately when both are measured.
Common Measurement Errors
- Arching the thoracic or lumbar spine at end range.
- Letting the elbow open beyond 90 degrees.
- Failing to keep the shoulder abducted at the same angle throughout the test.
Cobb Angle Pro Workflow
- Choose Shoulder External Rotation and set the supine 90/90 baseline.
- Use forearm-mounted sensor capture or clinician-held overlay mode.
- Save side, dominance, symptoms, and active or passive measurement status.
References
- Ellenbecker TS, Roetert EP, Bailie DS, et al. Glenohumeral joint internal and external rotation range of motion in elite tennis players. J Athletic Training. 1996;31(4):305-310.
- Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. 5th ed. F.A. Davis Company; 2016.