What is the appropriate workup for right shoulder pain and when should magnetic resonance imaging (MRI) be performed?

Workup for Right Shoulder Pain

Start with plain radiographs (X-rays) of the shoulder in all cases of shoulder pain, regardless of etiology, then proceed to MRI or ultrasound based on specific clinical findings and radiograph results 1.

Initial Imaging: Always Start with X-rays

Plain radiography is the mandatory first imaging study for any shoulder pain presentation 1. This should include at minimum three views: anteroposterior (AP) in internal and external rotation, plus an axillary or scapula-Y view 2. The axillary view is critical—glenohumeral and acromioclavicular dislocations can be completely missed on AP views alone 2.

Key point: Obtain upright radiographs when possible, as shoulder malalignment can be underrepresented on supine films 2.

When to Proceed to MRI: Clinical Scenario-Based Algorithm

Scenario 1: Normal or Nonspecific X-rays + Suspected Occult Fracture

• Order: MRI shoulder without contrast OR CT without contrast 1
• Rationale: MRI demonstrates bone marrow edema from trauma and identifies soft tissue pathology (rotator cuff, labral tears). CT provides superior detail for subtle nondisplaced fractures 1

Scenario 2: X-rays Show Fracture (Proximal Humerus, Scapula, or Clavicle)

• Order: CT without contrast as next study 1
• Exception: If rotator cuff injury is suspected AND patient is NOT planned for surgical fracture fixation, MRI without contrast is appropriate 1
• Rationale: MRI is inferior to CT for evaluating complex fracture patterns 1

Scenario 3: Clinical Exam Suggests Dislocation or Instability

• Order: MRI shoulder without contrast 1
• Rationale: In acute dislocation/instability, post-traumatic joint effusion or hemarthrosis provides natural contrast for visualizing soft tissue structures—no arthrography needed 1
• Alternative: CT without contrast may be appropriate if MRI assessment of bone loss is limited 1

Scenario 4: Clinical Exam Suggests Labral Tear

• Order: MRI without contrast (preferred in acute trauma) OR MR arthrography 1
• Timing matters: In acute trauma, joint effusion provides sufficient visualization—MRI without contrast is preferred. In subacute/chronic settings (when effusion has resolved), MR arthrography becomes the reference standard 1
• Alternative: CT arthrography if MRI contraindicated 1

Scenario 5: Clinical Exam Suggests Rotator Cuff Tear

• Order: MRI shoulder without contrast OR ultrasound 1
• These are equivalent alternatives—only order one 1

Choose MRI over ultrasound when:

• Large body habitus 1
• Restricted range of motion from acute pain 1
• Suspicion of other intra-articular pathology (labral tears) 1
• Previous proximal humeral hardware causing MRI artifacts—then ultrasound is preferred 1

Performance: Both modalities show 90-91% sensitivity and 93-95% specificity for full-thickness rotator cuff tears 1. However, ultrasound has conflicting evidence for partial-thickness tears and variable interobserver agreement 1.

Common Pitfalls to Avoid

1. Don't skip the axillary view on initial X-rays—dislocations are frequently missed without it 2

2. Don't order MR arthrography in acute trauma—the natural joint effusion/hemarthrosis makes invasive arthrography unnecessary and adds risk without benefit 1

3. Don't order MRI as the first study—radiographs must come first to identify fractures and dislocations, which are the primary management concerns 1, 2

4. Don't assume ultrasound can replace MRI for all pathology—ultrasound is inferior for partial-thickness rotator cuff tears and intra-articular pathology beyond the rotator cuff 1, 2

5. Don't order CT for soft tissue evaluation—CT is inferior to MRI for essentially all soft-tissue shoulder injuries 2

Special Considerations

MRI without contrast is generally the best soft tissue modality for labral, ligamentous, cartilage, and rotator cuff pathology, particularly in recent trauma 1. It has high sensitivity and specificity for full-thickness rotator cuff tears, though lower sensitivity than MR arthrography for partial-thickness tears 1.

MR arthrography is considered the gold standard for traumatic shoulder pain overall 2, superior to non-contrast MRI for intra-articular pathology (SLAP tears, labroligamentous injuries, partial rotator cuff tears) 2. However, the invasive nature makes it suboptimal as an initial study 2, and the acute trauma setting with natural effusion negates its advantage 1.