What is the best course of action for a patient with a known case of Rheumatoid Arthritis (RA) presenting with acute knee pain, swelling, redness, effusion, and a synovial fluid analysis showing leukocytosis, who is also febrile and tender on examination?

Management of Acute Knee Pain in a Patient with Rheumatoid Arthritis

IV antibiotics should be initiated immediately for this patient with RA presenting with acute knee pain, swelling, redness, fever, and synovial fluid WBC of 35,000, as this clinical picture is highly suggestive of septic arthritis requiring urgent treatment to prevent joint destruction and systemic complications. 1, 2

Diagnostic Assessment

The patient's presentation strongly suggests septic arthritis based on:

• Acute onset of knee pain, swelling, redness, and effusion
• Fever and tenderness on examination
• Synovial fluid WBC count of 35,000 cells/mm³
• Known rheumatoid arthritis (a risk factor for septic arthritis)

While patients with RA can experience flares, the combination of these findings, particularly the elevated synovial fluid WBC count and fever, points toward an infectious etiology rather than an RA flare alone 1, 2.

Treatment Algorithm

1. First-line treatment: IV antibiotics (Option A)

   • Begin empiric IV antibiotics immediately after synovial fluid collection
   • Initial coverage should target Staphylococcus aureus (most common pathogen) and other potential organisms 1, 2
   • Recommended regimens:
     • Vancomycin for gram-positive coverage (especially if MRSA is a concern)
     • Consider adding gram-negative coverage with ceftazidime or an aminoglycoside if gram stain is negative 1

2. Joint drainage

   • Arthrocentesis for initial drainage and diagnostic purposes
   • Consider surgical drainage (arthroscopy or arthrotomy) if inadequate response to initial drainage and antibiotics 3

3. Avoid intra-articular steroids (Option C)

   • Contraindicated in suspected septic arthritis as they may worsen infection 4
   • Only appropriate after infection has been definitively ruled out

4. Role of systemic steroids and NSAIDs

   • High-dose IV steroids (Option B) are not appropriate as first-line treatment for suspected septic arthritis
   • NSAIDs (Option D) alone are insufficient for treating septic arthritis but may be used as adjunctive therapy for pain control 5

Rationale for IV Antibiotics as First Choice

1. Mortality and morbidity considerations:

   • Untreated septic arthritis has mortality rates of 11-15% 2
   • Delayed antibiotic treatment increases risk of permanent joint damage and disability 1, 2

2. Diagnostic uncertainty:

   • Even when RA flare is suspected, the high synovial WBC count (35,000) and fever warrant empiric antibiotic coverage until cultures return 1, 2
   • Synovial fluid WBC >50,000 is typical for septic arthritis, but lower counts don't rule it out, especially in immunocompromised patients or those on immunosuppressive medications 1

3. Risk factors:

   • RA itself is a significant risk factor for septic arthritis due to:
     • Immunosuppressive medications
     • Joint damage from underlying disease
     • Increased frequency of procedures 5, 2

Common Pitfalls to Avoid

1. Mistaking septic arthritis for an RA flare

   • Both can present with joint pain and swelling
   • Fever and markedly elevated synovial fluid WBC count favor infection 5, 2

2. Delaying antibiotics while awaiting culture results

   • Empiric therapy should begin immediately after fluid collection 1, 2

3. Using intra-articular steroids when infection hasn't been ruled out

   • Can worsen infection and lead to rapid joint destruction 4

4. Relying solely on NSAIDs or systemic steroids

   • Inadequate for treating bacterial joint infection 1, 2

After the acute infection is controlled, the patient's RA management should be reassessed, potentially with DMARD therapy as recommended by the European League Against Rheumatism 4, 5.