What is the role of ultrasound imaging in diagnosing and treating shoulder pain?

Ultrasound Imaging for Shoulder Pain

Primary Diagnostic Role

Ultrasound is highly appropriate (rated 9/9 by the American College of Radiology) for evaluating rotator cuff pathology and biceps tendon disorders when performed by experienced operators, but has significant limitations for acute trauma, deep structures, and bone pathology. 1, 2

When Ultrasound is Most Useful

Rotator Cuff Evaluation

• Ultrasound achieves equivalent diagnostic accuracy to MRI for rotator cuff tears when performed by skilled operators 1, 2
• Particularly effective for detecting full-thickness tears, tendinitis, and calcific tendinopathy 3, 4
• Useful for post-operative assessment of rotator cuff integrity, including after shoulder replacement 1
• Can evaluate tendon retraction, though MRI provides superior assessment of muscle atrophy and fatty infiltration 1, 2

Biceps Tendon and Superficial Structures

• Excellent for evaluating long head of biceps tendon pathology including tenosynovitis, tendonitis, tears, and displacement 1, 4
• Effective for assessing acromioclavicular joint abnormalities 1, 4
• Can detect subacromial-subdeltoid bursitis 4, 5

Dynamic Assessment

• Ultrasound is the only imaging modality that allows real-time dynamic evaluation, which is critical for assessing impingement syndromes 3

Significant Limitations

Acute Trauma Setting

• Ultrasound has limited usefulness in acute shoulder pain that cannot be localized to the rotator cuff or biceps tendon 1
• While proximal humerus fracture detection has been described, ultrasound is generally limited in evaluating bone due to acoustic shadowing 1
• Ultrasound is inferior to MRI for assessing labroligamentous injuries, osseous pathology, and comprehensive rotator cuff evaluation in trauma 1
• One study showed 40% of patients with nonspecific shoulder pain had no significant pathology on ultrasound, highlighting its limitations as a screening tool 1

Deep Structures

• Cannot adequately evaluate labral tears, capsular structures, or glenohumeral ligaments 1
• Limited assessment of bone marrow, deep soft tissues, and intra-articular pathology 1, 4
• Operator-dependent with significant variability in diagnostic accuracy 1, 3

Therapeutic Applications

Ultrasound-Guided Interventions

• Highly appropriate (rated 9/9) for guiding arthrocentesis in suspected septic arthritis 1
• Effective for therapeutic corticosteroid injections in subacromial-subdeltoid bursitis 5
• Useful for guided treatment of calcific tendinopathy using single- or double-needle approaches 5
• Can guide platelet-rich plasma injections for degenerative tendinopathy 5
• Facilitates suprascapular nerve blocks for chronic shoulder pain 5

Clinical Decision Algorithm

Use Ultrasound When:

• Suspected isolated rotator cuff tear in older patients (>35 years) 1
• Evaluating biceps tendon pathology 1, 4
• Guiding therapeutic injections or aspirations 1, 5
• Assessing post-operative rotator cuff integrity 1
• Dynamic evaluation of impingement is needed 3

Do NOT Rely on Ultrasound Alone When:

• Acute trauma with nonspecific pain or concern for fracture—proceed directly to radiographs, then MRI or CT as indicated 1
• Suspected labral tears or glenohumeral instability—MRI or MR arthrography is required 1
• Patient age <35 years with instability symptoms—MR arthrography is preferred 1
• Noncontributory ultrasound in persistent pain—maintain low threshold for MRI 1

Important Caveats

A critical pitfall: recent evidence shows ultrasound-based classification of shoulder pathology does not predict medium-term outcomes or guide treatment selection 6. This suggests ultrasound's role should focus on confirming specific suspected diagnoses rather than broad screening, particularly when clinical examination already localizes pathology to rotator cuff or biceps structures.

The 2025 ACR guidelines emphasize that ultrasound "offers minimal value except in cases where an isolated rotator cuff tear is suspected" and "tends to overlook osseous and soft tissue injuries associated with shoulder instability or bony contusion" 1. This represents a more conservative stance than earlier guidelines.

Equipment quality and standardized scanning protocols are mandatory for reliable results 3, 4. Without experienced operators and high-quality equipment, diagnostic accuracy drops significantly.