How should I evaluate and manage left shoulder pain?

Evaluation and Management of Left Shoulder Pain

Begin with plain radiographs (AP views in internal and external rotation plus axillary or scapular Y view) to exclude fracture, dislocation, or significant arthritis, then proceed to MRI shoulder without IV contrast if rotator cuff pathology is suspected and conservative management has failed after 6-12 weeks or if clinical features suggest a full-thickness tear. 1, 2

Initial Clinical Assessment

Key Historical Features to Elicit:

• Mechanism of injury: Traumatic fall on outstretched arm increases likelihood of full-thickness rotator cuff tear 1
• Pain characteristics: Sharp/burning pain suggests radicular origin, while dull, diffuse, aching pain indicates tendinitis 3
• Night pain severity: Severe night pain is characteristic of full-thickness tears 1
• Age and activity level: Patients >60 years with weakness on resisted external rotation have higher risk of full-thickness tears 2

Critical Physical Examination Maneuvers:

• Empty can test (supraspinatus): Positive test indicates supraspinatus involvement and suggests full-thickness tear 1
• Drop arm test: Inability to slowly lower arm from 90° abduction suggests massive rotator cuff tear 2
• Range of motion assessment: Loss of both active AND passive ROM suggests adhesive capsulitis or glenohumeral arthritis, while preserved passive ROM with limited active ROM suggests rotator cuff pathology 4
• Resisted external rotation strength: Significant weakness suggests full-thickness tear 2

Imaging Algorithm

Step 1: Plain Radiographs (Mandatory First Step)

• Obtain three views: AP internal rotation, AP external rotation, and axillary or scapular Y view 1, 2
• Must be performed standing because poor shoulder alignment may be underestimated supine 2
• Purpose: Rule out fracture (occurs in up to 40% of trauma cases), dislocation, significant arthritis, or calcific tendinitis before advanced imaging 1, 2

Critical Pitfall: Failure to obtain axillary or scapular Y views can result in missed glenohumeral and AC dislocations that appear normal on AP views alone 1

Step 2: MRI Without IV Contrast (Primary Advanced Imaging)

The American College of Radiology recommends MRI shoulder without IV contrast as the optimal imaging modality for evaluating suspected rotator cuff pathology. 1

Indications for MRI:

• Failed conservative management after 6-12 weeks of appropriate physical therapy 2
• Clinical features suggesting full-thickness tear (positive empty can test, severe night pain, significant weakness, age >60 years) 1, 2
• Surgical planning is being considered 2

Diagnostic Performance:

• Sensitivity: 90-95% for full-thickness tears 1, 2
• Specificity: 90-95% for full-thickness tears 1, 2
• Superior for assessing tendon retraction, muscle atrophy, and fatty infiltration—critical factors guiding surgical decisions 1, 2

Why NOT intravenous contrast: Standard IV gadolinium provides no additional diagnostic benefit for rotator cuff evaluation and unnecessarily exposes patients to contrast-related risks 1

Step 3: MR Arthrography (Reserved for Specific Situations)

Reserve MR arthrography only when:

• Non-contrast MRI yields equivocal findings for partial-thickness tears 1, 2
• High clinical suspicion for labral injury exists 1, 2
• Patient is young (<35 years) with instability concerns 1

Important Note: In acute trauma with post-traumatic effusion, the joint is already distended, negating the advantage of arthrography—use non-contrast MRI instead 1

Alternative: Ultrasound (Limited Role)

Ultrasound may be considered when:

• MRI is contraindicated 2
• Proximal humeral hardware would cause MRI artifact 2
• Resource-limited settings 5

Limitations:

• Variable inter-observer agreement for partial-thickness tears 1, 2
• Highly operator-dependent 1
• Performance limited by acute pain restricting range of motion 1
• Less reliable for intra-articular pathology (labral tears, cartilage injury) 1

Diagnostic Performance: Sensitivity 90-91% and specificity 93-95% for full-thickness tears (comparable to MRI), but poor for partial-thickness tears 1, 2

Initial Conservative Management

For most shoulder pain without red flags:

• NSAIDs (oral non-steroidal anti-inflammatory drugs) 6
• Acetaminophen 6
• Directed physical therapy emphasizing rotator cuff, periscapular muscles, and core strengthening with capsular flexibility exercises 1, 2
• Subacromial corticosteroid injections may be considered for subacromial impingement, though evidence is insufficient for glenohumeral arthritis 2

Duration: Trial of conservative management for 6-12 weeks before proceeding to advanced imaging, unless clinical features suggest full-thickness tear 2

Surgical Referral Criteria

Refer to orthopedic surgery when:

• Full-thickness tear with tendon retraction, muscle atrophy, or fatty infiltration on MRI 2
• Massive traumatic tears requiring prompt surgical referral for optimal functional outcomes 2
• Unstable or significantly displaced fractures 2
• Joint instability or dislocations 2

Critical Pitfall: Do not proceed directly to orthopedic referral without advanced imaging—MRI is essential to confirm diagnosis, characterize tear extent and quality of remaining tendon, and guide appropriate treatment planning 1

Key Differential Diagnoses to Consider

• Glenohumeral instability and labral tears 1
• Acromioclavicular joint pathology 1
• Adhesive capsulitis (loss of both active and passive ROM) 1, 4
• Proximal humerus fractures (occur in up to 40% of trauma cases) 1
• Clavicle and scapula fractures 1
• Calcific tendinitis (visible on plain radiographs) 2

Modalities to Avoid

• Non-contrast CT: Cannot assess rotator cuff pathology in the acute setting and should not be used for soft-tissue evaluation 1, 2
• FDG-PET/CT and bone scans: Not routinely used for rotator cuff tears as they cannot describe tear extent or degree of atrophy 1