How should prepatellar bursitis be managed, including conservative therapy, ultrasound‑guided aspiration, antibiotics for septic bursitis, and indications for surgical bursectomy?

Management of Prepatellar Bursitis

Initial management of prepatellar bursitis should begin with aspiration to distinguish septic from aseptic cases, followed by conservative therapy with rest, NSAIDs, immobilization, and padding for aseptic cases, while septic cases require antibiotics with or without drainage procedures.

Diagnostic Approach

The critical first step is differentiating septic from aseptic bursitis through bursal fluid aspiration and analysis 1, 2. This distinction is essential because:

• Bursal fluid with >1000 cells/mm³ indicates septic bursitis and requires immediate antibiotic therapy 2
• Serous fluid content supports conservative management, while purulent aspirate necessitates more aggressive intervention 1
• Septic bursitis is frequently misdiagnosed as aseptic bursitis (occurred in 8 of 25 cases in one series), leading to treatment delays 2
• Repeated aspiration may be necessary in elusive cases, as illustrated by cases where crystals or bacteria were only detected on third aspiration 3

Clinical Features Suggesting Septic Bursitis

Prepatellar septic bursitis presents more aggressively than olecranon bursitis with 4:

• Fever (71% vs 48%)
• Leukocytosis (76% vs 52%)
• Surrounding cellulitis (59% vs 48%)
• Bacteremia (25% vs 0%)

Staphylococcus aureus causes 87.5% of septic bursitis cases, with 76% being penicillin-resistant 4, 2.

Management of Aseptic Prepatellar Bursitis

Initial Conservative Treatment

Immobilization with splinting for comfort and inflammation reduction should be implemented immediately 5. The comprehensive conservative approach includes:

• RICE protocol (Rest, Ice, Compression, Elevation) continued at home 5
• NSAIDs for pain relief and anti-inflammatory effect 5, 6
• Padding to protect the knee during activities, particularly important for chronic microtraumatic bursitis 6
• Compression to prevent fluid reaccumulation 1

Corticosteroid Injection

Corticosteroid instillation may be considered for persistent cases with serous aspirate, though high-quality evidence for benefit is lacking 6, 1. This should be:

• Performed with strict aseptic technique 6
• Reserved for selected cases that fail initial conservative management 1

Follow-up Strategy

Arrange follow-up within 1-2 weeks to assess treatment response 5. The management algorithm should include:

• Referral to orthopedics or rheumatology if symptoms persist despite 2-3 weeks of conservative management 5
• Patient education on warning signs of infection requiring immediate return to care 5
• Proper dosing instructions for prescribed NSAIDs 5

Management of Septic Prepatellar Bursitis

Antibiotic Therapy

Intravenous antibiotics targeting penicillin-resistant Staphylococcus aureus are the cornerstone of treatment 4, 2. The antibiotic regimen should:

• Cover penicillin-resistant S. aureus (76% resistance rate) 2
• Be administered intravenously initially, with average duration of 11 days (range 5-21 days) 4
• Continue until clinical resolution is achieved 4

Oral antibiotic therapy can be successful unless the infection is extensive or underlying bursal disease exists 2.

Drainage Procedures

The drainage approach depends on aspirate characteristics and clinical severity 1:

Needle Aspiration with Antibiotics

95% of septic bursitis cases resolve successfully without open surgical drainage when treated with prompt antibiotics and aspiration 4. This approach:

• Should be the initial intervention for most cases 4, 2
• Requires repeated aspirations as needed 4
• Results in no functional impairment, serious complications, or recurrences when properly executed 4

Percutaneous Suction-Irrigation System

For severe cases requiring continuous drainage, percutaneous tube placement with suction-drainage and local antibiotic irrigation is highly effective 7. This technique:

• Involves irrigation with 1% kanamycin and 0.1% polymyxin solution 7
• Controlled infection in 100% of cases (12/12) in one series 7
• Reduced antibiotic treatment duration to average 19 days versus 24 days without suction-irrigation 7
• Resulted in no complications or recurrences 7

Surgical Bursectomy

Open surgical drainage (bursotomy with incision and drainage, or bursectomy) should be reserved for 1:

• Purulent aspirate that fails conservative management with antibiotics and aspiration
• Extensive infections
• Underlying bursal disease complicating treatment 2

Common Pitfalls to Avoid

• Do not assume aseptic bursitis based on clinical appearance alone—always aspirate to confirm 2
• Do not use penicillin empirically—76% of S. aureus isolates are resistant 2
• Do not perform corticosteroid injection without first ruling out infection through aspiration and culture 6, 1
• Do not proceed directly to surgical drainage—95% of cases resolve with antibiotics and aspiration alone 4