What is the best way to distinguish between Rotator Cuff Tendinitis (RCT) and adhesive capsulitis?

Distinguishing Between Rotator Cuff Tendinitis (RCT) and Adhesive Capsulitis

The most effective way to distinguish between rotator cuff tendinitis and adhesive capsulitis is through a combination of specific physical examination maneuvers and targeted imaging studies, with MRI being the gold standard when clinical findings are inconclusive.

Clinical Examination Differences

Rotator Cuff Tendinitis

• Pain is typically well-localized and patients often describe it as "sharp" or "stabbing" 1
• Pain is reproducible with specific tendon loading maneuvers like the Hawkins' test (92% sensitive) and Neer's test (88% sensitive) 1
• Range of motion is often limited but primarily due to pain rather than mechanical restriction 1
• Tenderness is well-localized to the affected tendon, commonly at the supraspinatus insertion 1
• Pain is typically activity-related and improves with rest 1

Adhesive Capsulitis

• Pain is more diffuse and accompanied by progressive limitation of both active and passive glenohumeral motion in all directions 2
• Characteristic "capsular pattern" restriction with greater limitation of external rotation and abduction 2
• Pain at rest and night pain are more common 2
• Limitation of motion persists even under anesthesia (true mechanical restriction) 3
• Often has a characteristic clinical course with freezing, frozen, and thawing phases 2

Imaging Findings

Radiographs

• Initial radiographs are often normal in both conditions but can help rule out other pathologies 1
• In RCT, may show sclerosis or spur formation of acromion or calcific tendinosis 1
• In adhesive capsulitis, radiographs are typically normal but may show osteopenia due to disuse 3

Ultrasound

• Highly effective for RCT: shows tendon thickening, decreased echogenicity, and can detect moderate to full-thickness tears 1
• In adhesive capsulitis: may show thickening of the coracohumeral ligament and joint capsule, and reduced subacromial-subdeltoid bursa mobility 4
• Operator-dependent but useful for guiding injections in both conditions 1

MRI

• Gold standard for differentiating between the conditions when clinical examination is inconclusive 1
• For RCT: shows tendon signal abnormalities, thickening, and partial or full-thickness tears with high sensitivity (95%) and specificity (95%) 1
• For adhesive capsulitis: characteristic findings include thickening of the joint capsule and coracohumeral ligament, obliteration of the rotator interval fat pad (100% specific), and capsular contracture 3, 4

Key Distinguishing Features

• Motion Pattern: In adhesive capsulitis, both active and passive range of motion are equally limited in all directions, whereas in RCT, passive motion is often preserved but painful 2
• MR Arthrography: Shows poor capsular distension and extravasation of contrast in adhesive capsulitis, which is not seen in isolated RCT 4
• Combined Pathology: Approximately 62% of patients with presumed adhesive capsulitis may have some form of supraspinatus tendon pathology, making differentiation challenging 5
• Response to Treatment: RCT typically responds well to tendon-specific interventions, while adhesive capsulitis may require more aggressive interventions to address capsular restriction 1

Common Pitfalls to Avoid

• Assuming all shoulder pain with limited motion is adhesive capsulitis; approximately one-third of adhesive capsulitis patients have concomitant rotator cuff pathology 5
• Failing to recognize that routine glenohumeral exploration during arthroscopic procedures increases the risk of developing adhesive capsulitis (odds ratio 5.60) 6
• Overreliance on a single diagnostic test; the diagnosis should be based on a combination of clinical findings and appropriate imaging 1
• Misdiagnosing other conditions that can mimic these presentations, such as glenohumeral arthritis, biceps tendinopathy, or subacromial bursitis 2

Diagnostic Algorithm

1. Perform specific physical examination maneuvers:

   • If pain is reproduced with Hawkins' and Neer's tests with preserved passive range of motion → suspect RCT 1
   • If both active and passive motion are equally limited in all planes, especially external rotation → suspect adhesive capsulitis 2

2. Initial imaging with plain radiographs to rule out other pathologies 1

3. If diagnosis remains unclear:

   • Ultrasound if available expertise exists (excellent for RCT evaluation) 1
   • MRI without contrast for suspected RCT or combined pathology 1
   • MR arthrography for suspected adhesive capsulitis or in younger patients (<35 years) 1

4. Consider the natural history and progression of symptoms:

   • Gradual onset with activity-related pain suggests RCT 1
   • Progressive stiffening with pain at rest suggests adhesive capsulitis 2