Introduction
Adhesive capsulitis, also known as frozen shoulder, is a condition characterized by chronic inflammation, fibrosis, and contracture of the joint capsule leading to painful restriction of shoulder movements.
Although the diagnosis is primarily clinical, radiology — especially MRI — plays an important role in confirming the diagnosis, excluding mimics, and assessing severity.
Plain Radiograph (X-Ray)
- Usually normal.
- May show osteopenia (disuse) in chronic cases.
- Excludes differential diagnoses such as osteoarthritis or calcific tendinitis.
Ultrasound Findings
- Often nonspecific.
- May show thickened coracohumeral ligament.
- Useful mainly to rule out rotator cuff tears or bursitis.
MRI Findings (Modality of Choice)
Capsule & Ligaments
- Thickened coracohumeral ligament (>4 mm).
- Thickening of joint capsule at the rotator interval and axillary recess.
- Obliteration of fat in the rotator interval (normally bright on T1).
Joint Space & Synovium
- Decreased joint volume due to capsular contracture.
- Synovial enhancement after contrast (active inflammatory phase).
- Axillary pouch appears narrowed and thickened.
Other Features
- Increased T2/STIR signal in the rotator interval (inflammatory edema).
- No labral tear or significant cartilage damage (helps exclude arthritis).
Key Imaging Signs
- “Thickened coracohumeral ligament” = most consistent MRI sign.
- “Axillary recess contracture” = hallmark feature.
- “Loss of fat in rotator interval” = supportive finding.
Differential Diagnosis
- Rotator cuff tear (fluid-filled gap in tendon, retraction).
- Glenohumeral osteoarthritis (joint space narrowing, osteophytes).
- Calcific tendinitis (dense calcifications on X-ray/USG).
- Septic arthritis (joint effusion, marrow edema).
📊 Differentiating Adhesive Capsulitis from Other Causes of Shoulder Pain
| Feature | Adhesive Capsulitis (Frozen Shoulder) | Rotator Cuff Tear | Glenohumeral Osteoarthritis |
|---|---|---|---|
| Clinical Presentation | Pain + progressive restriction of active & passive ROM | Pain, weakness, limited active ROM (passive ROM preserved) | Chronic pain, crepitus, decreased ROM |
| X-Ray | Usually normal (may show disuse osteopenia) | Normal (unless calcific tendinitis coexists) | Joint space narrowing, osteophytes, subchondral sclerosis |
| Ultrasound | Thickened coracohumeral ligament; nonspecific | Hypoechoic tendon gap, fluid, tendon retraction | May show osteophytes, irregular cartilage |
| MRI – Capsule/Ligaments | Thickened coracohumeral ligament; thickened joint capsule at axillary recess | Normal capsule | Capsular osteophytes, capsular hypertrophy |
| MRI – Rotator Interval | Obliterated fat in rotator interval (low T1 signal) | Intact (unless massive tear) | Normal or distorted by osteophytes |
| MRI – Axillary Recess | Contracted, thickened, reduced volume | Normal | May be narrowed by osteophytes |
| MRI – Tendons | Usually normal (secondary bursitis may be seen) | Full/partial tear, tendon retraction, muscle atrophy | Tendons intact, may show degenerative changes |
| Enhancement (Post-contrast) | Synovial enhancement (active phase) | Enhancement around tear margins | Mild synovitis possible |
Teaching Points
- Adhesive capsulitis = fibrotic, contracted capsule → restricted movement.
- MRI is the gold standard for confirmation.
- Look for coracohumeral ligament thickening + axillary recess contracture.
- Radiology mainly supports clinical diagnosis and excludes mimics.
Conclusion
Adhesive capsulitis is a common cause of shoulder pain and stiffness. While clinical diagnosis is key, MRI provides characteristic findings that support diagnosis and help rule out other causes of restricted shoulder movement.
