What is the approach to diagnosing and managing a patient with right shoulder pain, including differential diagnosis (DDX), physical exam maneuvers, and necessary workup?

Diagnostic Approach to Right Shoulder Pain

Initial Red Flag Assessment

Begin by immediately ruling out life-threatening or urgent conditions before proceeding with musculoskeletal evaluation. 1

Critical red flags requiring urgent evaluation or referral include:

• Fever with joint effusion (septic arthritis) 1
• Acute neurologic deficits (nerve injury, cervical pathology) 1
• Chest pain, shortness of breath, or unusual fatigue (cardiac or pulmonary referred pain) 1, 2
• Acute trauma with deformity (fracture or dislocation) 1

Age-Stratified Differential Diagnosis

Patient age fundamentally changes your diagnostic priorities:

Under 35 Years

Primary concerns are:

• Labral tears (SLAP lesions) 1
• Glenohumeral instability with history of recurrent subluxation or "dead arm" sensation 1, 3
• Mechanical symptoms suggesting intra-articular pathology 1

Over 50 Years

Primary concerns are:

• Rotator cuff tears (partial or complete) 3
• Glenohumeral osteoarthritis with gradual pain and loss of motion 3
• Acromioclavicular osteoarthritis 3
• Adhesive capsulitis (especially with diabetes or thyroid disorders) 3

Systematic Physical Examination

Inspection and Palpation

• Observe for muscle atrophy in supraspinatus and infraspinatus fossae (suggests chronic rotator cuff pathology) 4
• Assess scapular position and movement for winging or dyskinesia 4
• Palpate acromioclavicular joint, sternoclavicular joint, and bicipital groove for focal tenderness 4
• Identify swelling, warmth, or crepitus indicating inflammation 4

Range of Motion Testing

Position patient sitting with 90° elbow flexion:

• Active and passive forward flexion (normal 0-180°) 4
• External rotation (normal 0-90°) 4
• Internal rotation (assess ability to reach up the back) 4
• Restricted passive range of motion in all planes suggests adhesive capsulitis 3

Rotator Cuff Strength Testing

For rotator cuff tears, use this clinical decision rule: pain with overhead activity + weakness on empty can test + weakness on external rotation + positive impingement sign. 3

Specific tests:

• Supraspinatus: Empty can test (Jobe's test) 4
• Infraspinatus/teres minor: Resisted external rotation 4
• Subscapularis: Lift-off test or belly press test 4
• Deltoid: Resisted abduction 4

Instability Testing (Under 40 Years)

• Apprehension test: Positive suggests anterior instability 3
• Relocation test: Relief with posterior pressure confirms instability 3

Acromioclavicular Joint Testing

• Cross-body adduction test: Pain indicates AC joint pathology 3
• Direct AC joint tenderness with superior shoulder pain 3

Imaging Algorithm

Step 1: Plain Radiographs (Always First)

Obtain plain radiographs as the initial imaging for ALL patients with shoulder pain, regardless of mechanism. 1

Minimum 3 views required:

• Anteroposterior (AP) in internal and external rotation 1
• Grashey view 1
• Axillary or scapular Y view 1

Plain radiographs help identify:

• Massive rotator cuff tears 3
• Fractures 1
• Dislocations 1
• Glenohumeral or AC osteoarthritis 3

Step 2: Advanced Imaging Based on Clinical Suspicion

If fracture identified on radiographs:

• CT without contrast to characterize fracture complexity and aid surgical planning 1

If suspected rotator cuff tear (age >35):

• MRI without contrast OR ultrasound are equivalent first-line studies 4, 1
• Choice depends on local expertise and availability 1
• Both have high appropriateness ratings for rotator cuff pathology 4

If suspected labral tear or instability (age <35):

• MR arthrography is the reference standard in subacute/chronic settings 1
• MRI without contrast preferred in acute trauma 1
• CT without contrast when bone loss assessment is critical for surgical planning 1

If suspected adhesive capsulitis:

• Clinical diagnosis based on restricted passive ROM in all planes 3
• Imaging typically not needed unless diagnosis unclear 3

If suspected AC joint arthritis:

• Plain radiographs usually sufficient 3

Common Diagnostic Pitfalls to Avoid

Do not dismiss neuropathic symptoms (electric shock sensations, allodynia) as "normal" pain—these require specific evaluation for nerve pathology. 1

• Do not skip initial radiographs before advanced imaging 1
• Do not order MR arthrography in acute postoperative settings—standard MRI without contrast is appropriate 5, 1
• Do not assume all shoulder pain is musculoskeletal—consider pulmonary pathology if patient has cough, fever, shortness of breath, or thoracic pain 2
• Do not rely solely on clinical tests for rotator cuff diagnosis—they have limited specificity when used in isolation 3

Arriving at the Correct Diagnosis

Integrate history, age, physical examination findings, and imaging in a systematic approach:

1. Rule out red flags first (septic arthritis, cardiac/pulmonary referred pain, acute neurologic deficits) 1, 2

2. Stratify by age: Under 35 think instability/labral tears; over 50 think rotator cuff/arthritis 1, 3

3. Use clinical decision rules: For rotator cuff tears, require multiple positive findings (overhead pain + weakness + impingement) 3

4. Always obtain plain radiographs first before advanced imaging 1

5. Match imaging to clinical suspicion: MRI/ultrasound for rotator cuff, MR arthrography for labral tears, CT for fracture characterization 1

6. Consider adhesive capsulitis when passive ROM is globally restricted, especially with diabetes or thyroid disease 3

7. Assess for neuropathic features (electric shock sensations) that require neuromodulating medications rather than just NSAIDs 5, 1