What is the therapy for septic arthritis?

From the Guidelines

Septic arthritis requires prompt treatment with antibiotics and joint drainage to prevent joint destruction, with a recommended treatment duration of 6 weeks for prosthetic joint infections and 2 weeks for native joint septic arthritis, as supported by the most recent study 1. Initial therapy should include empiric broad-spectrum antibiotics that cover common causative organisms like Staphylococcus aureus, streptococci, and gram-negative bacteria.

• For adults, a reasonable regimen is vancomycin 15-20 mg/kg IV every 12 hours (to cover MRSA) plus ceftriaxone 2g IV daily or cefepime 2g IV every 8 hours (for gram-negative coverage).
• For children, cefazolin 100-150 mg/kg/day divided every 8 hours is appropriate, with vancomycin added if MRSA is suspected. Joint drainage is essential and can be accomplished through arthrocentesis, arthroscopy, or open surgical drainage depending on the joint involved and severity.
• Drainage should be performed as soon as possible, with samples sent for culture, Gram stain, cell count, and crystal analysis. Once culture results return (typically 48-72 hours), antibiotics should be narrowed to target the specific organism. Total treatment duration may vary depending on the type of joint infection, with 6 weeks being adequate for prosthetic joint infections and 2 weeks for native joint septic arthritis, as shown in the study 1. Joint immobilization during the acute phase followed by early mobilization once pain improves helps preserve joint function. Treatment success is monitored through clinical improvement, normalization of inflammatory markers (ESR, CRP), and repeat joint aspiration if needed, as recommended by previous guidelines 1.

From the Research

Diagnosis of Septic Arthritis

• The diagnosis of septic arthritis is based on clinical suspicion, physical examination findings, and synovial fluid studies 2, 3.
• Risk factors for septic arthritis include age older than 80 years, diabetes mellitus, rheumatoid arthritis, recent joint surgery, hip or knee prosthesis, skin infection, and immunosuppressive medication use 3.
• Synovial fluid white blood cell count is usually greater than 50,000 per mm3 in patients with septic arthritis, and isolation of the causative agent through synovial fluid culture is essential before selecting antibiotic therapy 2.

Treatment of Septic Arthritis

• The treatment of septic arthritis involves a combination of antibiotics and the prompt removal of purulent material from the affected joint 2, 4.
• Empiric antibiotic therapy should be initiated if there is clinical concern for septic arthritis, and the choice of antibiotics should be guided by the patient's age, synovial fluid gram stain results, and any preexisting conditions 2, 3, 5.
• The total duration of therapy ranges from two to six weeks, but certain infections may require longer courses 3, 6.
• Oral antibiotics can be given in most cases, and treatment can be safely switched from intravenous to oral after 2-4 days 6.

Special Considerations

• Patients with prosthetic joint infection require special consideration, and the intraarticular cutoff values for infection may be as low as 1,100 white blood cells per mm3 with a neutrophil differential of greater than 64 percent 2.
• Neonates, patients with immunodeficiency, and cases caused by methicillin-resistant S. aureus may require a different approach to treatment 6.
• Long-term follow-up is necessary to check for relapses and to assess the outcome of any residual joint damage 5.