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Differentiating Adhesive Capsulitis, Rotator Cuff Tear, and Glenohumeral Osteoarthritis in a 55-Year-Old Diabetic

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1. Clinical Overview and Why Diabetes Matters

• Harrison's Principles of Internal Medicine 22E, p.3018
• Miller's Review of Orthopaedics 9th Ed.

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2. History - The First Discriminator

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3. Physical Examination - The Most Important Step

Range of Motion: The Key Differentiator

"The pathognomonic sign [of frozen shoulder] is loss of active external rotation... classically, active ROM and passive ROM are equivalent."

• Bailey & Love's Short Practice of Surgery 28th Ed., p.552

"Two other causes of selective loss of external rotation are glenohumeral osteoarthritis and a locked posterior shoulder dislocation; for this reason, radiographs must be obtained before a diagnosis of frozen shoulder is made."

• Miller's Review of Orthopaedics 9th Ed.

Specific Tests

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4. Radiological Differentiation

Plain X-ray (Always the First Step)

"Radiographs are normal and distinguish [frozen shoulder] from osteoarthritis."

• Bailey & Love's Short Practice of Surgery 28th Ed.

MRI - The Definitive Second-Line Investigation

"MRI may show thickening of the glenohumeral joint capsule along the axillary pouch, thickening of the CHL, obliteration of the subcoracoid fat triangle, and rotator interval synovitis; however, none of these findings are pathognomonic."

• Miller's Review of Orthopaedics 9th Ed.

Ultrasound

• Useful for rotator cuff tear - dynamic assessment, cost-effective, good sensitivity for full-thickness tears
• In adhesive capsulitis: power Doppler may show increased vascularity at rotator interval in early disease
• Poor for assessing capsular contracture and cartilage

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5. Staging of Adhesive Capsulitis (Unique to This Diagnosis)

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6. Diagnostic Approach - Step by Step

55-year-old diabetic, 6 months shoulder pain + restricted ROM
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Step 1: Plain X-ray (AP, Y-view, axillary)
    - Normal? → Consider AC or RC tear / early frozen shoulder
    - OA changes (joint space loss, osteophytes)? → Glenohumeral OA
    - Superior humeral migration? → Massive RC tear
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Step 2: Physical exam - active vs. passive ROM
    - Active = Passive (global loss, especially ER)? → Adhesive capsulitis
    - Active < Passive (weakness, positive drop arm/lag signs)? → Rotator cuff tear
    - Crepitus + bony end-feel? → Glenohumeral OA
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Step 3: Ultrasound
    - Tear visible? → Rotator cuff tear confirmed
    - No tear? → Consider adhesive capsulitis vs. OA
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Step 4: MRI (with gadolinium if capsular pathology suspected)
    - CHL thickening + rotator interval changes + intact tendons? → Adhesive capsulitis
    - Tendon discontinuity + fluid? → Rotator cuff tear
    - Cartilage loss + subchondral changes? → Glenohumeral OA

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7. Summary Comparison Table

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Practical Pearl for This Case

• Start with plain X-ray to rule out OA and posterior dislocation
• Test passive ER at the side - if it is severely limited and equals active ER, frozen shoulder is most likely
• Test active abduction against gravity - if weak and limited despite preserved passive ROM, suspect rotator cuff tear
• Order MRI if diagnosis is uncertain or if planned treatment requires confirmation (e.g., before manipulation under anaesthesia or steroid injection)