Internal rotation of the shoulder is the movement that turns the upper arm inward toward the body and across the trunk (e.g., reaching behind the back), occurring mainly at the glenohumeral joint. External rotation turns the arm outward, away from the body (e.g., reaching to scratch the back of the head). Both actions are produced by coordinated rotator cuff and scapular muscles.

Have the patient sit or stand with the shoulder adducted and the elbow flexed to 90°. For external rotation, ask them to rotate the forearm away from the body (or reach toward the head). For internal rotation, ask them to rotate the forearm toward the abdomen or reach behind the back and note the highest vertebral level reached. Measure angles with a goniometer (axis at the olecranon, moving arm along the forearm) and compare sides.

Shoulder external rotation is the outward turning of the upper arm (humerus) so the forearm and palm move away from the body. It’s mainly produced by rotator cuff muscles—especially infraspinatus and teres minor—and the posterior deltoid. External rotation is essential for overhead activities, throwing, reaching behind the head, and is assessed when evaluating shoulder mobility and injury.

The three standard shoulder X‑ray views are: anteroposterior (AP) view — shows the glenohumeral joint and proximal humerus; scapular Y (lateral) view — demonstrates scapular anatomy and detects dislocation or fracture alignment; and axillary view — visualizes the glenohumeral relationship and joint space for assessing dislocation, glenoid rim fractures, and arthropathy. These three complement each other for comprehensive assessment.

Pain with shoulder internal rotation can arise from subscapularis or rotator-cuff tendinopathy/tears, posterior labral or SLAP lesions, impingement or biceps tendinopathy, adhesive capsulitis (frozen shoulder) limiting motion, glenohumeral osteoarthritis, or acromioclavicular joint problems. Overuse, acute injury, or instability often contribute. Clinical exam and imaging help pinpoint the exact cause and guide treatment.

Internal rotation: rotating a limb toward the body’s midline — e.g., turning the arm so the palm faces the stomach or rotating the thigh so the toes point inward. External rotation: rotating a limb away from the midline — e.g., rotating the arm so the palm faces outward or placing the hand behind the head, or turning the thigh so the toes point outward.