Subacromial Bursitis

Comprehensive Clinical Guide: Subacromial Bursitis

Subacromial bursitis represents one of the most prevalent clinical entities encountered in orthopedic and sports medicine practice. It is a hallmark of shoulder pathology, characterized by acute or chronic inflammation of the subacromial bursa—a thin, fluid-filled sac situated between the acromion process of the scapula and the underlying rotator cuff tendons. This guide provides an exhaustive clinical overview of the etiology, diagnostic criteria, and management frameworks for this condition.

1. Clinical Definition and Overview

Subacromial bursitis is an inflammatory condition characterized by the thickening, hypervascularization, and subsequent pain production of the subacromial bursa. Anatomically, the bursa serves as a critical gliding mechanism, facilitating smooth movement of the supraspinatus tendon beneath the coracoacromial arch during shoulder abduction and elevation.

When the space between the humeral head and the acromion (the subacromial space) becomes compromised, the bursa undergoes mechanical impingement. This leads to the release of inflammatory cytokines, resulting in pain, restricted range of motion (ROM), and localized tenderness. It is frequently categorized under the broader umbrella of "Subacromial Impingement Syndrome" (SIS).

2. Pathophysiology and Mechanism of Injury

The pathophysiology of subacromial bursitis is typically multifactorial, involving a transition from mechanical irritation to biochemical inflammation.

The Mechanism of Impingement

The subacromial space, normally measuring 10–13 mm in healthy adults, can be narrowed by several factors:
* Anatomic Variations: Type II or Type III (hooked) acromion shapes.
* Osteophyte Formation: Degenerative changes at the acromioclavicular (AC) joint.
* Postural Dysfunction: Scapular dyskinesis resulting in premature acromial tipping during elevation.

Biochemical Cascade

1. Mechanical Friction: Repetitive overhead activity causes shearing forces on the bursal wall.
2. Microtrauma: Repeated impingement leads to micro-tears in the bursal lining.
3. Inflammatory Response: Activation of synovial cells leads to the production of prostaglandins, leukotrienes, and interleukins.
4. Fibrosis: Chronic, untreated bursitis may lead to thickening of the bursa, further reducing the subacromial space and creating a self-perpetuating cycle of impingement.

3. Clinical Staging and Grading

Orthopedic literature often utilizes the Neer Staging system to describe the progression of subacromial pathology:

4. Standard Presentation and Symptomatology

Patients presenting with subacromial bursitis typically report a specific clinical constellation:

• Pain Location: Lateral shoulder pain, often radiating toward the deltoid insertion.
• Aggravating Factors: Overhead reaching, lifting objects away from the body, and sleeping on the affected side.
• Painful Arc: Characterized by pain during active abduction between 60° and 120°.
• Night Pain: Significant disruption of sleep, common in the acute phase of inflammation.

5. Differential Diagnosis

Distinguishing subacromial bursitis from other shoulder pathologies is critical, as treatment pathways differ significantly.

6. Key Diagnostic Tests and Clinical Assessment

Physical Examination

• Neer Impingement Test: Passive forced flexion of the humerus in internal rotation. Positive if pain is elicited at the superior limit of elevation.
• Hawkins-Kennedy Test: Forward flexion to 90°, followed by forced internal rotation. This compresses the bursa against the acromion.
• Empty Can (Jobe) Test: Tests the integrity of the supraspinatus; often painful in bursitis.

Imaging Modalities

• Radiography (X-Ray): Initial assessment to identify acromial morphology (Bigliani classification) and superior migration of the humeral head.
• Ultrasound (US): Highly sensitive for bursal thickening, fluid collection, and dynamic assessment of impingement.
• Magnetic Resonance Imaging (MRI): The gold standard for ruling out full-thickness rotator cuff tears or labral pathology.

7. Risks, Contraindications, and Management

Risks of Untreated Bursitis

• Secondary Adhesive Capsulitis: Avoidance of movement due to pain leads to joint capsule thickening.
• Rotator Cuff Atrophy: Prolonged pain prevents muscle recruitment, leading to disuse atrophy.
• Chronic Calcific Tendinopathy: Deposition of calcium salts within the tendons.

Contraindications for Corticosteroid Injections

While subacromial injections are common, they are contraindicated in:
* Suspected septic bursitis (fever, erythema, extreme warmth).
* Recent history of shoulder trauma/fracture.
* Active infection in the skin overlying the injection site.
* Systemic instability (uncontrolled diabetes).

8. Long-Term Prognosis

The prognosis for subacromial bursitis is generally excellent with conservative intervention. Approximately 80–90% of patients respond to a structured regimen of physiotherapy focusing on:
1. Scapular stabilization: Strengthening the serratus anterior and lower trapezius.
2. Rotator cuff strengthening: Focusing on eccentric loading.
3. Postural correction: Addressing thoracic kyphosis.

Failure to improve after 3–6 months of physical therapy warrants re-evaluation for subacromial decompression surgery (acromioplasty).

9. Frequently Asked Questions (FAQ)

Q1: Is subacromial bursitis permanent?
No, it is a reversible inflammatory condition. With appropriate loading, rest, and rehabilitation, the inflammation typically resolves.

Q2: Can I continue to exercise with shoulder pain?
Modify your activity. Avoid overhead movements until the inflammatory phase subsides, but continue non-aggravating exercises to maintain mobility.

Q3: How long does it take for a cortisone injection to work?
Most patients report significant relief within 48 to 72 hours, though the effect can vary based on the chronicity of the inflammation.

Q4: Is surgery always required?
Surgery is rarely the first line of treatment. It is reserved for patients who have failed at least 3–6 months of intensive, supervised physical therapy.

Q5: Why does my shoulder hurt more at night?
When lying down, the gravitational pull on the arm and the lack of muscle activation can lead to increased joint compression and local inflammatory pooling.

Q6: What is the difference between bursitis and tendonitis?
Bursitis is the inflammation of the fluid sac; tendonitis is the inflammation of the tendon itself. Often, they coexist as part of the impingement syndrome.

Q7: Can posture affect my shoulder?
Absolutely. Forward-rounded shoulders (kyphotic posture) tilt the acromion forward, physically narrowing the subacromial space.

Q8: What is "frozen shoulder" and is it the same?
No. Frozen shoulder (adhesive capsulitis) involves a tightened joint capsule. Bursitis is primarily an inflammatory issue of the bursa.

Q9: Should I use ice or heat?
Use ice during the acute inflammatory phase (first 48-72 hours). Use heat for chronic stiffness to increase tissue extensibility before performing exercises.

Q10: Are there long-term complications of bursitis?
If left untreated, chronic bursitis can lead to "cuff-tear arthropathy," where the rotator cuff wears away, causing the humeral head to migrate superiorly and erode the acromion.

10. Conclusion

Subacromial bursitis requires a methodical approach that balances symptom management with mechanical correction. By identifying the root cause—whether it be anatomical, postural, or behavioral—clinicians can move beyond temporary relief to long-term resolution. As with all orthopedic conditions, patient compliance with a progressive rehabilitation program remains the most critical factor in achieving a successful outcome.

Disclaimer: This document is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare professional regarding a medical condition.