What are the recommended assessments for evaluating a patient suspected of having shoulder impingement syndrome?

Assessment Recommendations for Shoulder Impingement Syndrome

Begin with standard radiographs (anteroposterior views in internal and external rotation plus axillary or scapula-Y view) followed by targeted physical examination maneuvers, with MRI or ultrasound reserved for cases where imaging is needed to characterize soft tissue pathology or guide treatment decisions. 1

Initial Imaging Assessment

Standard radiographs are the mandatory first imaging study and should include three views: 1, 2

• Anteroposterior view in internal rotation
• Anteroposterior view in external rotation
• Axillary or scapula-Y view (critical—do not skip this orthogonal view)

Radiographs serve to exclude fractures, evaluate bone morphology (acromial shape, os acromiale), assess joint space narrowing, and identify calcific tendinitis. 1

Look specifically for muscle atrophy in the supraspinatus and infraspinatus fossae on inspection, which suggests chronic rotator cuff pathology. 1

Physical Examination Maneuvers

Position the patient sitting with 90° elbow flexion and hand supinated resting on the thigh for baseline assessment. 1

Specific Impingement Tests

The Yocum maneuver demonstrates the highest sensitivity and accuracy for subacromial impingement syndrome. 3 This test involves the patient placing their hand on the opposite shoulder and elevating the elbow without raising the shoulder.

Additional examination components include: 1

• Active and passive range of motion assessment in all planes: forward flexion (0-180°), external rotation (0-90°), internal rotation (ability to reach up the back)
• Scapular position and movement assessment for winging or dyskinesia
• Palpation of the acromioclavicular joint, bicipital groove, and proximal humerus for tenderness

Rotator Cuff Strength Testing

Test individual rotator cuff muscles systematically: 1

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

Important caveat: Pain significantly inhibits strength testing results in impingement syndrome—patients may demonstrate 48-90% increases in strength parameters after subacromial anesthetic injection, making baseline strength assessment potentially misleading. 4 Consider diagnostic injection if strength deficits seem disproportionate to clinical presentation.

Advanced Imaging Indications

For suspected rotator cuff pathology after noncontributory radiographs, MRI without contrast or ultrasound are equivalent first-line studies with high appropriateness ratings. 1

When to Order MRI vs Ultrasound

MRI is superior for: 5

• Glenoid labral tears
• Subacromial bursal effusion/hypertrophy
• Joint capsule pathology
• Bone marrow edema
• Complex cases requiring comprehensive soft tissue evaluation

Ultrasound has comparable accuracy for: 5

• Rotator cuff tears (98.1% sensitivity)
• Biceps tendon pathology (100% sensitivity)
• Cost-effective initial assessment when local expertise is available

MRI should be prioritized when these structures (glenoid labrum, bursa, capsule) are determinants of shoulder disability and treatment planning. 5 Ultrasound is justifiable and cost-effective following plain radiographs in straightforward cases, with MRI reserved for more complex presentations. 6

Special Population Considerations

For athletes and overhead throwers, additionally assess shoulder motion, flexibility, strength, and other components of the kinetic chain. 1

Evaluate scapular dyskinesis specifically, as this may contribute to rotator cuff injury and impingement. 1

Diagnostic Algorithm Summary

1. Standard three-view radiographs (AP internal/external rotation + axillary/scapula-Y) 1, 2
2. Focused physical examination emphasizing Yocum test, rotator cuff strength testing, and scapular assessment 1, 3
3. Consider diagnostic subacromial injection if pain limits examination or strength assessment appears disproportionate 4
4. Order ultrasound or MRI based on need to characterize soft tissue pathology, local imaging expertise, and complexity of presentation 1, 5

Critical pitfall: Most physical examination maneuvers have low specificity despite acceptable sensitivity—imaging is recommended to better define shoulder lesions and avoid misdiagnosis. 3 Do not rely on physical examination alone for definitive diagnosis.