Frozen Shoulder vs. Rotator Cuff Tendinopathy
A comparison of two common causes of shoulder pain and dysfunction, differing in etiology, clinical presentation, examination findings, diagnostic approach, and management.
Frozen shoulder is characterized by progressive pain and global stiffness of the glenohumeral joint, with marked reduction in both active and passive range of motion, often affecting middle-aged adults and those with diabetes.
Rotator cuff tendinopathy is typically due to chronic overuse or degeneration of the rotator cuff tendons (especially the supraspinatus), presenting with pain aggravated by overhead activity, with preserved passive range of motion and weakness or pain on strength testing.
Comparison Table
| Feature | Frozen Shoulder (Adhesive Capsulitis) | Rotator Cuff Tendinopathy |
|---|---|---|
| Epidemiology | Lifetime prevalence 2–5%; peak in mid-50s; more common in women | Most common cause of shoulder pain; increases with age; affects manual laborers and athletes |
| Risk Factors | Diabetes, thyroid disease, dyslipidemia, immobilization, stroke, trauma | Repetitive overhead activity, older age, anatomic variants, scapular instability, diabetes, obesity |
| Pathophysiology | Inflammation and fibrosis of joint capsule; reduced joint volume | Tendon degeneration, microvascular insult, biomechanical overload |
| Clinical Presentation | Progressive severe pain (often at night), global stiffness, loss of both active and passive motion | Pain with overhead activity, night pain, weakness, pain on strength testing; passive motion usually preserved |
| Physical Exam | Marked reduction in active and passive ROM in ≥2 planes; firm, painful end to passive motion; mechanical restriction | Painful arc, positive Neer/Hawkins/Jobe tests, tenderness, weakness; passive ROM > active ROM |
| Diagnostic Approach | Clinical diagnosis; imaging to rule out other causes; injection test distinguishes from subacromial pathology | Clinical diagnosis; musculoskeletal ultrasound is gold standard; MRI for unclear cases or suspected tear |
| Imaging Findings | MRI: thickening/enhancement of capsule/ligaments; US: thickening of capsule/ligaments | US: tendon thickening, hypoechogenicity, calcifications; MRI: high-intensity signal, degeneration |
| Management | Gentle mobility exercises, intra-articular glucocorticoid injection, physical therapy; surgery for refractory cases | Physical therapy (mobility, strength, coordination), short course of NSAIDs, single glucocorticoid injection if needed; surgery if nonoperative therapy fails |
| Prognosis | Usually self-limited but may persist; risk of long-term disability, especially in diabetes | Risk of frozen shoulder and tendon tear if untreated; most improve with conservative management |
Key Distinguishing Features
- Frozen shoulder: marked loss of both active and passive ROM, mechanical restriction, often idiopathic or secondary to systemic disease or trauma
- Rotator cuff tendinopathy: pain with activity, preserved passive ROM, weakness or pain on strength testing, often due to overuse or degeneration
Which Is More Likely After a Vaccine?
Neither — shoulder bursitis (subdeltoid or subacromial) is the most likely shoulder pathology after vaccination.
- Shoulder bursitis is a recognized adverse effect of intramuscular deltoid vaccination, with an attributable risk of ~7.78 excess cases per million people vaccinated for influenza
- There is no evidence that frozen shoulder or rotator cuff tendinopathy are direct complications of vaccination
- Injection site reactions (pain, tenderness, swelling, limited arm movement) after vaccination are common but transient and do not represent tendinopathy or adhesive capsulitis
Clinical pearl: For patients presenting with shoulder pain after vaccination, consider shoulder bursitis as the most likely diagnosis. Use musculoskeletal ultrasound if there is persistent pain or limited motion.
Source: UpToDate — Frozen shoulder (adhesive capsulitis); Rotator cuff tendinopathy; Seasonal influenza vaccination in adults