What is the management of septic arthritis?

Management of Septic Arthritis

Septic arthritis requires immediate surgical drainage combined with empiric IV vancomycin, followed by culture-directed antibiotics for 3-4 weeks, as this dual approach prevents irreversible cartilage destruction that can occur within hours to days. 1, 2

Immediate Diagnostic Approach

Joint aspiration is the definitive diagnostic procedure and must be performed urgently unless the patient requires immediate operative intervention. 3, 1

• Synovial fluid white blood cell count ≥50,000 cells/mm³ is suggestive of septic arthritis, though this threshold is not absolute and can be influenced by various factors. 3, 1, 2
• Synovial fluid culture yields positive results in approximately 80% of non-gonococcal septic arthritis cases. 3, 1, 2
• If joint aspirate culture is positive, proceed directly to treatment without bone biopsy. 3
• If joint aspirate is negative but clinical suspicion remains high, obtain a percutaneous image-guided bone biopsy for culture. 3, 1, 2

Imaging Considerations

• Ultrasound is the initial imaging modality of choice, particularly for hip joints, to detect effusions and guide aspiration. 2
• MRI has high sensitivity for detecting joint effusions, soft tissue involvement, and concomitant osteomyelitis when clinical suspicion persists despite negative aspiration. 1, 2
• Elevated CRP and WBC count (including neutrophils and monocytes) support the diagnosis but are nonspecific. 2, 4

Surgical Management

All cases of septic arthritis require surgical drainage—this is non-negotiable. 1, 2

• For surgical emergencies (signs of sepsis, severe systemic toxicity), proceed directly to the operating room for arthrotomy, irrigation, and debridement with intraoperative cultures. 3, 1, 2
• For non-emergency cases, drainage can be accomplished through arthrocentesis, arthroscopic drainage, or open surgical debridement. 2
• Prosthetic joint infections require device removal whenever possible. 1
• If a prosthetic device cannot be removed and the isolate is Candida susceptible to fluconazole, chronic suppression with fluconazole 400 mg daily is recommended. 1

Antibiotic Therapy

Empiric Therapy (Start Immediately After Obtaining Cultures)

IV vancomycin is first-line empiric therapy for adults given the high prevalence of MRSA in septic arthritis. 1, 2, 4

• Adult dosing: Vancomycin 30-60 mg/kg/day IV in 2-4 divided doses, or 15 mg/kg IV every 6 hours. 2
• Pediatric dosing: Vancomycin 15 mg/kg/dose IV every 6 hours (40 mg/kg/day in 4 divided doses). 2
• Alternative empiric options for adults if MRSA is less likely: Linezolid 600 mg IV/PO every 12 hours, Daptomycin 6 mg/kg IV daily, or Teicoplanin 6-12 mg/kg IV every 12 hours for 3 doses then daily. 2
• For children, clindamycin 10-13 mg/kg/dose IV every 6-8 hours is an alternative if local clindamycin resistance is low. 1, 2

Culture-Directed Therapy

Switch antibiotics based on culture results and susceptibility testing:

• MSSA (Methicillin-Sensitive S. aureus): Switch to nafcillin or oxacillin 1-2 g IV every 4 hours, OR cefazolin 1 g IV every 8 hours, OR clindamycin 600 mg IV every 8 hours (if penicillin allergic). 2
• MRSA (Methicillin-Resistant S. aureus): Continue vancomycin as primary therapy. Consider adding rifampin 600 mg PO daily or 300-450 mg PO twice daily for enhanced bone and biofilm penetration. 1, 2
• Streptococcal infections: Penicillin G 20-24 million units IV daily (continuous infusion or divided doses), OR ceftriaxone 1-2 g IV every 24 hours. 2
• Polymicrobial infections require dual antibiotic coverage (e.g., linezolid for MRSA plus ciprofloxacin for Pseudomonas aeruginosa). 1, 2

Transition to Oral Therapy

Oral antibiotics are not inferior to IV therapy for most cases of septic arthritis. 2, 4

• Switch to oral antibiotics after 2-4 days if the patient is clinically improving, afebrile, and can tolerate oral intake. 2
• Oral options for MRSA (after initial IV therapy): Linezolid 600 mg PO every 12 hours, TMP-SMX (trimethoprim 4 mg/kg/dose) PO every 8-12 hours plus rifampin 600 mg PO daily, or fusidic acid 500 mg PO every 8 hours or 750 mg every 12 hours plus rifampin. 2

Duration of Therapy

The standard duration for uncomplicated bacterial septic arthritis is 3-4 weeks. 1, 2

• Recent evidence suggests 2 weeks may be adequate after surgical drainage in select cases (predominantly small joints). 2
• Prosthetic joint infections treated with debridement and implant retention require 12 weeks of antibiotics (superior to 6 weeks). 1, 2
• Hip prostheses with one-stage or two-stage exchange: 3 months total treatment. 2
• Knee prostheses with one-stage or two-stage exchange: 6 months total treatment. 2
• Candida septic arthritis: Fluconazole 400 mg daily for 6 weeks OR an echinocandin for 2 weeks followed by fluconazole 400 mg daily for at least 4 weeks. 1

Special Pathogen Considerations

Tailor your empiric coverage based on patient demographics and risk factors:

• Children <4 years: Consider Kingella kingae as a causative organism. 1, 2, 5
• Patients with sickle cell disease: Consider Salmonella species. 1, 2, 5
• Neonates: Group B streptococcus predominates. 5
• Gonococcal arthritis: Consider Neisseria gonorrhoeae based on sexual history and clinical presentation. 4, 6

Management of Concomitant Osteomyelitis

Concomitant osteomyelitis occurs in up to 30% of children with septic arthritis and requires longer antibiotic treatment. 1, 2

• MRI is the imaging modality of choice to detect concurrent osteomyelitis. 1
• Extend antibiotic duration beyond the standard 3-4 weeks when osteomyelitis is confirmed. 1, 2

Management of Persistent or Recurrent Symptoms

For persistent or recurrent joint swelling after completing oral antibiotics:

• Re-treat with another 4-week course of oral antibiotics OR 2-4 weeks of IV ceftriaxone. 1, 2
• Arthroscopic synovectomy may reduce the duration of joint inflammation in cases of persistent synovitis with significant pain or functional limitation. 1, 2
• If arthritis persists despite IV therapy and synovial fluid PCR is negative, consider symptomatic treatment with NSAIDs or DMARDs. 2

Critical Pitfalls and Caveats

• Negative joint aspirate culture does not rule out infection—maintain high clinical suspicion and consider percutaneous bone biopsy if needed. 3, 1, 2
• Do not give intra-articular corticosteroid injections during active infection. 2
• Avoid or discontinue antibiotics for an optimal period of 2 weeks before obtaining cultures if the clinical situation permits (though this is rarely feasible in acute septic arthritis). 3
• Monitor vancomycin trough levels and adjust dosing to avoid toxicity. 2
• Be vigilant for drug interactions and adverse effects in elderly patients receiving prolonged antibiotic therapy. 2
• All patients with candidemia should have a dilated retinal examination within the first week of therapy to establish if endophthalmitis is present. 1
• Monitor CRP and ESR to assess treatment response. 2

Why This Approach Matters

Bacterial proliferation within the joint space causes rapid cartilage damage through direct toxicity and inflammatory response—this destruction can occur within hours to days. 1, 5, 7

• Bacterial virulence factors (adhesins, toxins, biofilm formation) enable attachment to joint surfaces and persistence despite treatment. 5
• The exacerbated immune response (massive release of TNF-α, IL-1, IL-6) contributes equally or more to joint destruction than the bacteria themselves. 5, 7
• Mortality remains approximately 11% despite aggressive treatment, and MRSA-associated cases exhibit higher mortality, longer hospital stays, and poorer clinical outcomes compared to MSSA. 7, 4
• Delay in diagnosis and treatment results in permanent morbidity and mortality. 4, 8, 6