What is the initial imaging study for a patient with suspected adhesive capsulitis (frozen shoulder) and what are the subsequent imaging options if further evaluation is needed?

Imaging for Frozen Shoulder (Adhesive Capsulitis)

Initial Imaging Study

Standard shoulder radiography is the appropriate initial imaging study for suspected adhesive capsulitis, consisting of at least three views: anteroposterior (AP) projections in internal and external rotation plus an axillary or scapula-Y view, performed with the patient upright. 1, 2, 3

Purpose of Initial Radiographs

• Radiographs serve primarily to exclude common differential diagnoses rather than to diagnose adhesive capsulitis itself, which remains a clinical diagnosis 4, 5
• Key conditions to rule out include:
  • Glenohumeral or acromioclavicular osteoarthritis 4, 6
  • Calcific tendinitis 4, 6
  • Fractures or dislocations 1, 3
  • Rotator cuff arthropathy with superior humeral head migration 2

Critical Technical Requirements

• All three views are mandatory: AP views alone can misclassify acromioclavicular and glenohumeral pathology 1, 3
• Upright positioning is essential: supine radiography underrepresents shoulder malalignment 1, 2, 3
• The axillary or scapular Y view is vital for detecting joint alignment abnormalities that AP views miss 1, 3

Advanced Imaging When Diagnosis Remains Uncertain

If radiographs are normal but clinical suspicion for adhesive capsulitis persists or alternative diagnoses need exclusion:

MRI Without Contrast (Preferred Advanced Study)

MRI without intravenous contrast is the most appropriate next imaging study for confirming adhesive capsulitis when radiographs are noncontributory 4, 5, 6

Diagnostic MRI Findings for Adhesive Capsulitis:

• Capsule and synovium thickening >4mm (measured at the axillary recess) is 95% specific and 70% sensitive for adhesive capsulitis 7
• Coracohumeral ligament thickening yields high specificity for the diagnosis 5, 6
• Thickening of the inferior glenohumeral ligament 8, 6
• Obliteration of the rotator interval fat pad has 100% specificity for adhesive capsulitis 8
• Fibrosis of the subcoracoid fat triangle 6

When to Add Gadolinium:

• Intravenously administered gadolinium increases the sensitivity of MRI for detecting adhesive capsulitis 4
• MR arthrography can demonstrate extravasation of contrast outside joint recesses and poor capsular distension 8, 6

Ultrasound (Alternative Advanced Study)

High-resolution ultrasound is an appropriate alternative when MRI is contraindicated or unavailable 4, 8, 6

Ultrasound Findings:

• Capsular thickening at the axillary recess 8, 6
• Coracohumeral ligament thickening 8, 6
• Rotator interval abnormalities 8

Additional Ultrasound Advantages:

• Can guide intra-articular and periarticular therapeutic injections 8, 6
• Useful when proximal humeral hardware would create MRI artifacts 2

Imaging Modalities NOT Recommended

• CT has no role in adhesive capsulitis diagnosis due to radiation exposure and significantly lower sensitivity/specificity compared to MRI 4
• Fluoroscopy-guided arthrography has been replaced by MRI due to its invasiveness 4
• Standard arthrography is no longer recommended as a first-line diagnostic tool 4, 5

Common Pitfalls to Avoid

• Do not skip initial radiographs: Even when adhesive capsulitis is clinically obvious, radiographs are necessary to exclude mimicking conditions 3, 4, 6
• Do not rely on AP views alone: Orthogonal views prevent missed pathology 1, 3
• Do not assume self-resolution: Recent evidence shows persistent functional limitations if left untreated, challenging the traditional "wait and see" approach 5
• Recognize that adhesive capsulitis typically affects middle-aged women and has increased prevalence in patients with diabetes mellitus and hypothyroidism 4, 5