When is aspiration of prepatellar bursitis recommended?

Aspiration of Prepatellar Bursitis

Aspiration of prepatellar bursitis is strongly recommended when infection is suspected, as it provides both diagnostic information and therapeutic benefit by reducing pressure and pain.

Indications for Aspiration

Aspiration of prepatellar bursitis is indicated in the following scenarios:

1. Suspected septic (infectious) bursitis:

   • Presence of erythema, warmth, and tenderness over the bursa
   • Systemic symptoms such as fever
   • Recent trauma with skin break or history of occupational kneeling
   • Rapidly developing swelling and pain

2. Diagnostic purposes:

   • To differentiate between septic and non-septic bursitis
   • When clinical presentation is unclear
   • To guide appropriate antibiotic therapy

3. Therapeutic purposes:

   • To relieve pressure and pain
   • As part of initial management before considering more invasive procedures

Aspiration Procedure and Analysis

When performing aspiration of prepatellar bursitis:

• Obtain fluid for Gram stain, cell count with differential, and aerobic/anaerobic cultures 1
• Consider image guidance (ultrasound or fluoroscopy) for accurate needle placement and to reduce risk of complications 1
• Evaluate fluid characteristics:
  • Purulent fluid suggests infection
  • Serous fluid suggests non-infectious etiology

Management Algorithm Based on Aspiration Results

If Septic Bursitis is Confirmed:

1. Initial management:

   • Appropriate antibiotic therapy based on culture results
   • Consider repeat aspirations if fluid reaccumulates
   • Rest, compression, and immobilization 2

2. If conservative management fails:

   • Consider more invasive options such as:
     • Percutaneous suction-irrigation system placement 3
     • Surgical drainage or bursectomy for recalcitrant cases 2, 4

If Non-Septic Bursitis is Confirmed:

1. Conservative management:
   • Compression
   • Immobilization
   • Anti-inflammatory medications
   • Consider corticosteroid injection in selected cases 4

Important Considerations and Pitfalls

• Antibiotic timing: If infection is suspected and antibiotics have already been started, they should be discontinued for at least 2 weeks before aspiration to avoid false-negative cultures 1

• Repeat aspirations: If the first aspiration is negative but clinical suspicion for infection remains high, weekly repeat aspirations may be necessary 1

• Dry tap: The absence of fluid ("dry tap") during aspiration does not rule out infection 1

• Surgical risks: Be aware that surgical bursectomy carries risks of complications including skin necrosis and should be reserved for cases that fail conservative management 2

• Occupational factors: Patients who kneel at work may have higher rates of recurrence and persistent symptoms 5

Conclusion

Aspiration of prepatellar bursitis plays a crucial role in both diagnosis and treatment, particularly when infection is suspected. The procedure helps differentiate between septic and non-septic bursitis, guides appropriate antibiotic therapy, and provides symptomatic relief. Management should follow a stepwise approach based on aspiration results, with surgical intervention reserved for cases that fail conservative treatment.