The shoulder is the most mobile joint in the human body — and one of the most frequently imaged in emergency departments and outpatient orthopedics. With a range of motion that exceeds any other joint, it is also the most commonly dislocated major joint, accounting for approximately 50% of all dislocations seen in the ED. For the radiologic technologist, mastering shoulder positioning is not optional; it is one of the most frequently tested areas on the ARRT registry and a daily clinical skill.
This guide covers every standard shoulder projection you'll encounter: AP internal and external rotation, the Grashey (true AP) view, the scapular Y-view (trans-scapular lateral), and the axillary lateral — plus trauma protocols, centering points, evaluation criteria, and common pathology recognition. Whether you are a first-semester student or preparing for the registry, these are the projections you must know cold.
The shoulder girdle consists of three bones: the clavicle (anteriorly), the scapula (posteriorly), and the humerus. The glenohumeral joint is formed by the articulation of the humeral head with the shallow glenoid fossa of the scapula. Key landmarks for positioning include the coracoid process (anterior, inferior to the clavicle), the acromion (lateral extension of the scapular spine), and the acromioclavicular (AC) joint. The scapula rests on the posterior rib cage at an angle of approximately 30–45° to the coronal plane — this angle is critical to understanding why the Grashey view requires patient rotation.
The AP shoulder is the most commonly ordered projection and serves as the starting point for nearly every shoulder series. It is typically performed in two rotations to evaluate different aspects of the humeral head and glenohumeral joint.
Positioning: The patient is erect or supine with the affected shoulder positioned against the IR. The patient's arm is supinated (palm facing forward), and the elbow is slightly flexed. The epicondyles of the humerus are parallel to the IR. The CR is directed perpendicular to the IR, centered 1 inch (2.5 cm) inferior to the coracoid process. SID: 40 inches (100 cm).
Evaluation Criteria: The humeral head is seen in profile, and the greater tuberosity is visualized laterally along the humeral head margin. The lesser tuberosity is superimposed on the humeral head. The glenohumeral joint space is visible but the humeral head partially overlaps the glenoid. The axillary fat pad (when present) is distinguishable inferomedially. A properly positioned external rotation view projects the greater tuberosity laterally, giving the humeral head a characteristic "ball-on-a-stick" appearance.
Positioning: Same basic setup as the external rotation view, but the patient's arm is pronated (palm facing posteriorly or toward the thigh). The epicondyles are perpendicular to the IR. The CR is centered at the same point — 1 inch inferior to the coracoid process.
Evaluation Criteria: The lesser tuberosity is seen in profile medially, projecting over the humeral head. The greater tuberosity is superimposed on the humeral head, producing a more rounded, featureless contour. This view is particularly valuable for demonstrating the Hill-Sachs lesion — a compression fracture of the posterolateral humeral head that occurs following anterior shoulder dislocation. On the internal rotation view, a Hill-Sachs defect appears as a visible notch or flattening along the superior-lateral margin of the humeral head.
When a patient presents with a suspected shoulder dislocation, always start with the AP internal rotation view. Why? An anterior dislocation (95% of all shoulder dislocations) is most obvious on this projection — the humeral head will appear inferior and medial to the glenoid fossa. The external rotation view may be too painful for an acutely dislocated patient to achieve. Many protocols begin with AP internal rotation and the scapular Y-view before attempting external rotation.
The Grashey view — named after the American radiologist Dr. Stephen Grashey — is the true AP projection of the glenohumeral joint. Unlike the standard AP shoulder, which superimposes the humeral head over the glenoid, the Grashey view profiles the joint space by rotating the patient so the X-ray beam passes through the glenohumeral articulation tangentially.
The patient is positioned AP, then rotated 35–45° toward the affected shoulder (i.e., the affected shoulder is brought closer to the IR). Alternatively, some technologists prefer to perform this as a PA oblique projection by rotating the patient 35–45° away from the affected side. The arm is placed in external rotation (palm up), and the CR is directed perpendicular to the IR, centered at the glenohumeral joint — approximately 1–2 inches (2.5–5 cm) inferior and slightly medial to the coracoid process. SID: 40 inches (100 cm).
The key feature of a correctly positioned Grashey view is an open glenohumeral joint space. The humeral head should not overlap the glenoid fossa, and the joint space should appear as a sharp, narrow radiolucent curve. The anterior and posterior glenoid rims are superimposed, and the scapula is seen on-end, appearing as a dense opacity superimposed over the ribs. The coracoid process projects anteriorly and medially. The Grashey view is the preferred projection for evaluating glenohumeral joint space narrowing in osteoarthritis and for detecting subtle glenoid labral injuries.
A common ARRT question asks: "Which projection best demonstrates the glenohumeral joint space free of superimposition?" The answer is the Grashey method (true AP). Remember that the standard AP shoulder DOES superimpose the humeral head and glenoid — it is NOT a "true" AP of the joint because the scapula sits at a 30–45° angle to the coronal plane.
The scapular Y-view is one of the most important projections in the shoulder trauma series. It provides a lateral view of the scapula, creating a distinctive "Y" shape formed by the scapular body (vertical stem), the acromion (superior arm), and the coracoid process (anterior arm). The humeral head should be centered at the intersection of the Y when the glenohumeral joint is properly reduced.
The patient can be positioned AP oblique or PA oblique. The most common method is the AP oblique (anterior oblique) approach:
The scapula should appear as a true lateral view — the body of the scapula is seen on-end as a dense vertical opacity, while the acromion and coracoid process extend superiorly and anteriorly. The three bony processes form the Y shape. The humeral head should be superimposed over the center of the Y (the point where the three branches meet). If the humeral head is displaced inferiorly and anteriorly from the Y-intersection, suspect an anterior dislocation. If displaced posteriorly, suspect a posterior dislocation (much less common, ~2–4% of shoulder dislocations).
The scapular Y-view is also excellent for evaluating fractures of the scapular body, scapular neck, acromion, and coracoid process. Scapular fractures are relatively uncommon (0.5–1% of all fractures) and are typically caused by high-energy trauma such as motor vehicle collisions.
Insufficient rotation (less than 45°): The scapula is not perpendicular to the IR, resulting in an oblique rather than true lateral view of the Y. The humeral head appears displaced even when reduced. Over-rotation (more than 60°): The Y shape becomes distorted. Wrong centering: CR centered too high or too low misses the glenohumeral joint, requiring a repeat exposure. Always palpate the coracoid process and center 1 inch inferior.
The axillary lateral (also known as the axillary projection) evaluates the glenohumeral joint in a plane perpendicular to the AP view. It is the gold standard for confirming posterior shoulder dislocation and is excellent for demonstrating glenoid rim fractures, Hill-Sachs lesions, and os acromiale (an unfused acromial apophysis that can mimic fracture).
The patient is supine with the affected shoulder elevated approximately 3–4 inches (8–10 cm) on a radiolucent pad. The arm is abducted 70–90° from the body, depending on the patient's range of motion — this is the most important and most challenging aspect of the positioning. The elbow is flexed 90°, and the forearm is supported. The CR is directed through the axilla, angled 15–30° toward the sternoclavicular joint (medially and slightly cephalad). The IR is placed against the superior aspect of the shoulder, perpendicular to the CR. SID: 40 inches (100 cm).
For patients who cannot abduct the arm 90° due to pain or trauma, the Lawrence method can be used. The patient is supine, and the arm is abducted only as far as tolerated. The CR is directed 5–15° anteriorly and 5–15° medially, passing through the glenohumeral joint. The IR is placed against the lateral aspect of the shoulder.
The glenohumeral joint is visualized in profile with the humeral head centered within the glenoid fossa. The anterior and posterior glenoid rims should be superimposed or nearly superimposed. The coracoid process projects anteriorly, and the acromion projects superiorly. The axillary view provides a complete 360° assessment of the glenohumeral relationship when combined with the AP views and the scapular Y-view.
| Projection | Patient Position | CR Centering | Arm Position | Best For |
|---|---|---|---|---|
| AP External Rotation | Erect or supine, shoulder against IR | 1 inch inferior to coracoid | Supinated (palm up), epicondyles ∥ IR | Routine evaluation; greater tuberosity; humeral head profile |
| AP Internal Rotation | Erect or supine, shoulder against IR | 1 inch inferior to coracoid | Pronated (palm down/thigh), epicondyles ⟂ IR | Hill-Sachs lesions; anterior dislocation (trauma) |
| Grashey (True AP) | Rotated 35–45° toward affected side | Glenohumeral joint (1–2 in inferomedial to coracoid) | External rotation | Glenohumeral joint space; osteoarthritis; labral injuries |
| Scapular Y-View | 45–60° oblique, affected side toward IR | Scapulohumeral joint (coracoid) | Arm across chest or on opposite shoulder | Dislocation confirmation; scapular fractures; AC joint |
| Axillary Lateral | Supine, arm abducted 70–90° | Through axilla, 15–30° toward SC joint | Abducted, elbow flexed 90° | Posterior dislocation; glenoid rim fractures; os acromiale |
When a patient arrives in the emergency department with a suspected shoulder injury, the standard trauma series typically consists of three to four views. The exact protocol varies by institution, but the ARRT recognizes the following as the minimum acceptable trauma shoulder series:
The AP external rotation view is often added after reduction to assess the post-reduction position and evaluate for associated fractures (Hill-Sachs, Bankart lesions, greater tuberosity fractures).
1. The Grashey (true AP) requires 35–45° patient rotation toward the affected side — this aligns the scapular body parallel to the IR, opening the glenohumeral joint space.
2. The scapular Y-view requires 45–60° rotation so the scapula is perpendicular to the IR.
3. The axillary lateral requires 70–90° arm abduction — this is the most commonly missed positioning requirement on the registry.
4. A properly positioned humeral head on a Y-view sits at the intersection of the Y — displacement indicates dislocation.
5. The Stryker notch view is a special projection for demonstrating Hill-Sachs lesions when AP internal rotation is inconclusive.
As a radiologic technologist, you are responsible for recognizing abnormal findings even before the radiologist's report. Here are the key pathologies you must be able to identify on shoulder radiographs:
On the AP view, the humeral head is displaced inferiorly and medially (subcoracoid or subglenoid position). The AP internal rotation view shows the humeral head sitting below the glenoid. On the Y-view, the humeral head is displaced anteriorly from the Y-intersection. Associated injuries include Hill-Sachs lesions (posterolateral humeral head impaction fracture — best seen on AP internal rotation) and Bankart lesions (anteroinferior glenoid labrum tear — best seen on MRI arthrography, but a bony Bankart may be visible on the Grashey or axillary view as a small glenoid rim avulsion fracture).
Posterior dislocations are frequently missed on initial radiographs. On the AP view, the humeral head appears symmetrically rounded (the "light bulb sign") because the arm is fixed in internal rotation. The Y-view shows the humeral head displaced posteriorly from the Y-intersection. The axillary lateral is definitive, showing the humeral head sitting posterior to the glenoid fossa. A reverse Hill-Sachs lesion (impaction fracture of the anteromedial humeral head) may be present.
These are classified using the Neer classification system, which divides the proximal humerus into four segments: (1) articular head, (2) greater tuberosity, (3) lesser tuberosity, and (4) humeral shaft. A fracture is considered displaced if any segment is separated >1 cm or angulated >45°. The Grashey view is essential for evaluating articular surface involvement, while the axillary view best demonstrates tuberosity displacement.
Suspected AC joint injuries require either a dedicated AC joint series (AP both shoulders with weights) or can be evaluated on an AP shoulder that includes the AC joint. The Rockwood classification (Types I–VI) describes the degree of separation. On an AP view, compare the distance between the inferior aspect of the acromion and the superior aspect of the clavicle. Normal distance is 1–3 mm; widening >5 mm indicates injury.
Shoulder radiography requires careful attention to technical factors to produce diagnostic images:
Most shoulder projections use a 40-inch (100 cm) SID. However, the AC joint series (weight-bearing bilateral AP views) may use a 72-inch (180 cm) SID to reduce magnification and provide a more accurate comparison of AC joint alignment. Always check your department's protocol for AC joint imaging.
Radiation protection is paramount in shoulder radiography. The breast tissue lies within the primary beam field for many shoulder projections — particularly in female patients. Use these strategies to minimize dose while maintaining diagnostic quality:
Try these ARRT-style multiple choice questions based on this article. Click an option to check your answer — correct answers turn green, wrong ones turn red.