Diagnosing Adhesive Capsulitis (Frozen Shoulder)
Adhesive capsulitis is diagnosed clinically by demonstrating equal restriction of both active and passive range of motion in all planes, with external rotation being the most severely affected movement, followed by abduction. 1
Clinical Diagnostic Criteria
The diagnosis is primarily clinical and does not require imaging for confirmation 1:
- External (lateral) rotation is the most severely restricted movement and correlates strongly with the onset of shoulder pain 1, 2
- Both active and passive range of motion are equally restricted in all planes, which is the key distinguishing feature from other shoulder pathology 1, 2
- Abduction is severely restricted, particularly in the frozen stage 2
- Progressive stiffness develops gradually with stage-dependent pain 3, 4
Key Risk Factors to Identify
In your 40-70-year-old female patient, actively assess for these systemic conditions 1:
- Diabetes mellitus (strongly associated) 1, 5, 6
- Thyroid disease (hypothyroidism or hyperthyroidism) 1, 5, 6
- Recent shoulder immobilization or surgery 1
- Post-stroke hemiplegia (up to 67% incidence with combined motor, sensory, and visuoperceptual deficits) 2
- Polyarticular osteoarthritis 1
Critical Differential Diagnosis
You must actively exclude rotator cuff tears, as they can mimic similar stiffness and pain patterns 1. The key differentiating feature is:
- Rotator cuff syndrome shows preserved passive motion with weakness and pain primarily during active movement, whereas adhesive capsulitis shows equal restriction of both active and passive motion 1
- Rotator cuff pathology demonstrates focal weakness with decreased range during abduction with external or internal rotation, but passive motion remains relatively preserved 1
Other conditions to exclude include 1, 2:
- Degenerative joint disease or glenohumeral osteoarthritis 1, 2
- Crystal arthropathies 1, 2
- Septic arthritis 1, 2
- Calcific tendinitis 1
- Acromioclavicular joint disease 1
- Subacromial/subdeltoid bursitis 1
Role of Imaging
Plain radiographs are usually normal in adhesive capsulitis because the pathology involves capsular fibrosis and inflammation, not bony changes 7. However, they are useful to exclude other causes:
- X-rays are primarily useful to exclude fractures, dislocations, glenohumeral arthritis, rotator cuff arthropathy, or calcific tendinitis 7
- Standard shoulder radiographic series will demonstrate normal bony anatomy and alignment 7
When imaging is needed for unclear cases 1:
- MRI without contrast is the most appropriate advanced imaging test (rated 9 by the American College of Radiology), particularly when radiographs are noncontributory 1
- Coracohumeral ligament thickening on MRI yields high specificity for adhesive capsulitis 6
- Ultrasound is equally appropriate depending on local expertise 1
- Bone scintigraphy shows increased periarticular radiotracer uptake but provides limited anatomic detail and is rarely used clinically 1, 2, 7
Common Diagnostic Pitfalls
- Do not overlook that shoulder pain in certain populations may be due to adhesive capsulitis rather than disease relapse (e.g., in polymyalgia rheumatica patients) 1
- In post-stroke patients, improper handling during rehabilitation, such as overhead pulley exercises, can worsen adhesive capsulitis 1, 2
- Approximately one-third of acute stroke patients have shoulder tissue injury (effusion, tendinopathy, or rotator cuff tears) that may contribute to capsulitis 2
Clinical Staging Recognition
Understanding the three stages helps confirm diagnosis 3, 4: