Internal rotation of the shoulder turns the arm toward the body—bringing the palm or forearm inward or the back of the hand toward the back—at the glenohumeral joint. Muscles: subscapularis, pectoralis major, latissimus dorsi and teres major. External rotation turns the arm outward away from the body—rotating the palm or forearm laterally—primarily using infraspinatus, teres minor and posterior deltoid.

To test shoulder internal and external rotation: have the patient sit or lie supine with the shoulder abducted to 90° and elbow flexed 90°, or with the arm at the side. Stabilize the scapula, then have the patient actively (or examiner passively) externally rotate (forearm away from midline) and internally rotate (forearm toward abdomen or behind the back). Measure with a goniometer, compare sides, and note pain, stiffness, or weakness. Apley scratch test assesses combined rotation.

Shoulder external rotation is the outward turning of the arm at the shoulder joint, rotating the humerus away from the body so the forearm and palm face laterally or posteriorly. It’s primarily produced by the infraspinatus and teres minor (with posterior deltoid), and is essential for reaching behind, throwing and dressing; weakness or pain often reflects rotator-cuff or joint problems.

The three standard shoulder X‑ray views are: (1) Anteroposterior (AP) — taken in external (and sometimes internal) rotation to assess the glenohumeral joint and tuberosities; (2) Axillary (axial) view — visualizes the glenoid‑humeral relationship, useful for detecting dislocations; (3) Scapular Y (lateral) view — shows the scapular body, acromion, coracoid and helps identify fractures or dislocation.

Pain with shoulder internal rotation can arise from rotator cuff (especially subscapularis) tendonitis or tears, impingement, adhesive capsulitis (frozen shoulder), glenohumeral osteoarthritis, labral injury, biceps or AC joint pathology, or cervical spine referral. Overuse, acute trauma, or degenerative changes increase risk. Evaluation by a clinician with imaging and specific tests helps identify the exact cause and guide treatment.

Internal rotation: turning a limb toward the body’s midline — for example, rotating the shoulder so the palm turns posteriorly when reaching behind your back, or rotating the hip so the toes point inward. External rotation: turning a limb away from the midline — for example, rotating the shoulder so the palm faces forward or rotating the hip so the toes point outward, like crossing one leg over the other.