What is the treatment for septic arthritis?

Treatment of Septic Arthritis

Septic arthritis requires immediate surgical debridement combined with IV vancomycin as first-line empiric antibiotic therapy, followed by culture-directed treatment for 3-4 weeks in uncomplicated cases. 1, 2

Immediate Management

Surgical Intervention (Priority #1)

• Drainage of the joint space must always be performed through arthrocentesis, arthroscopic drainage, or open surgical debridement—this is non-negotiable. 1, 2
• Arthrotomy, irrigation, and debridement are the standard surgical interventions. 1, 2
• Surgical emergencies require immediate debridement with intraoperative cultures rather than waiting for aspiration results. 1
• The choice between arthroscopic vs. open drainage depends on infection stage: stage I infections rarely need repeat procedures (5%), stage II need repeat arthroscopy in 52%, and stage III in 75%. 3

Empiric Antibiotic Therapy (Start Immediately After Cultures)

• IV vancomycin is the first-line empiric therapy for adults, dosed at 15 mg/kg IV every 6 hours (or 30-60 mg/kg/day in 2-4 divided doses). 1, 2, 4
• This covers MRSA, which is increasingly common and represents 42% of identified organisms in septic arthritis. 1, 3
• Vancomycin must be infused over at least 60 minutes to avoid rapid-infusion reactions including hypotension and cardiac arrest. 4
• Monitor vancomycin trough levels and renal function due to nephrotoxicity risk. 1, 4

Pediatric Empiric Therapy

• Vancomycin 15 mg/kg/dose IV every 6 hours (40 mg/kg/day in 4 divided doses). 1
• Infuse over 60 minutes in neonates to reduce risk of bilirubin encephalopathy. 1
• Alternative: Clindamycin 10-13 mg/kg/dose IV every 6-8 hours if local clindamycin resistance is low. 1, 2

Culture-Directed Definitive Therapy

For Methicillin-Susceptible Staphylococcus aureus (MSSA)

• Switch from vancomycin to nafcillin or oxacillin 1-2 g IV every 4 hours, OR cefazolin 1 g IV every 8 hours. 1
• Oxacillin should be administered carefully in elderly patients due to thrombophlebitis risk. 5
• If penicillin allergic: Clindamycin 600 mg IV every 8 hours. 1

For Methicillin-Resistant Staphylococcus aureus (MRSA)

• Continue vancomycin as primary therapy. 1, 2
• Consider adding rifampin 600 mg PO daily or 300-450 mg PO twice daily for enhanced bone and biofilm penetration, despite vancomycin's poor bone penetration concerns. 1, 2
• Alternative agents: 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. 1

For Streptococcal Infections

• Penicillin G 20-24 million units IV daily (continuous infusion or divided doses), OR ceftriaxone 1-2 g IV every 24 hours. 1
• Ceftriaxone must not be administered simultaneously with calcium-containing IV solutions due to precipitation risk. 6

For Polymicrobial Infections

• Dual antibiotic coverage is mandatory, for example: linezolid for MRSA plus ciprofloxacin for Pseudomonas aeruginosa. 1, 2

Duration of Therapy

Standard Duration

• 3-4 weeks for uncomplicated bacterial arthritis after surgical drainage. 1, 2
• Recent evidence suggests 2 weeks may be adequate in select cases (predominantly small joints) after successful surgical drainage. 1
• Therapy should continue at least 48 hours after the patient becomes afebrile, asymptomatic, and cultures are negative. 5

Extended Duration Scenarios

• Prosthetic joint infections: 12 weeks is superior to 6 weeks when treated with debridement and implant retention. 1, 2
• Hip prostheses with one-stage or two-stage exchange: 3 months total. 1
• Knee prostheses with one-stage or two-stage exchange: 6 months total. 1
• Concomitant osteomyelitis (occurs in up to 30% of children) requires longer treatment. 1, 2

Route Transition

• Oral antibiotics are not inferior to IV therapy for most cases of septic arthritis. 1
• Switch to oral can be made after 2-4 days if the patient is clinically improving, afebrile, and can tolerate oral intake. 1
• Oral options for MRSA (after initial IV): 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 plus rifampin. 1

Special Pathogen Considerations

Age-Specific Pathogens

• Children <4 years: Consider Kingella kingae as a causative organism. 1, 2, 7
• Neonates: Group B streptococcus is common. 7
• Patients with sickle cell disease: Consider Salmonella species. 1, 2, 7

Gonococcal Arthritis

• Single intramuscular dose of ceftriaxone 250 mg for uncomplicated gonococcal infections. 1
• If Chlamydia trachomatis is suspected, add appropriate antichlamydial coverage as ceftriaxone has no activity against this organism. 6

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. 2
• Prosthetic device removal is recommended; if removal impossible, chronic suppression with fluconazole 400 mg daily (if susceptible). 2
• All patients with candidemia require dilated retinal examination within the first week to establish if endophthalmitis is present. 2

Critical Pitfalls and Caveats

Diagnostic Pitfalls

• Negative joint aspirate culture does not rule out infection—synovial fluid culture is positive in only approximately 80% of non-gonococcal cases. 1, 2
• Consider percutaneous bone biopsy if joint aspirate is negative but clinical suspicion remains high. 1, 2
• Synovial fluid WBC count ≥50,000 cells/mm³ is suggestive of septic arthritis. 1, 2

Treatment Pitfalls

• Do not delay surgical drainage—bacterial proliferation rapidly causes irreversible cartilage damage through direct toxicity and inflammatory response. 1, 2, 7
• Mortality rates are significant: 2-15% overall, with 90-day mortality of 7% in patients ≤79 years and 22-69% in those >79 years. 8, 9
• Poor functional outcomes (amputation, arthrodesis, prosthetic surgery) occur in 24-33% of patients. 9
• Monitor for vancomycin nephrotoxicity and ototoxicity, especially with underlying renal impairment, concomitant nephrotoxic drugs, or excessive doses. 4

Persistent Infection Management

• For persistent or recurrent joint swelling after 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 inflammation duration in persistent synovitis with significant pain or functional limitation. 1, 2
• If arthritis persists despite IV therapy and synovial fluid PCR is negative: Symptomatic treatment with NSAIDs or DMARDs. 1