Treatment of septic arthritis should be initiated with empiric antibiotics as soon as initial blood and synovial fluid cultures have been drawn and should be based on the findings of the Gram stain (Table 46.2). Initial treatment generally begins with vancomycin for Gram-positive cocci. If Gram-negative cocci are found, treatment is typically begun with ceftriaxone. When Gram-negative rods are present, ceftazidime, cefepime, piperacillin/tazobactam, or carbapenems are considered as first-line treatment unless the patient has a penicillin or cephalosporin allergy in which case aztreonam or fluoroquinolones can be considered as alternatives. If the Gram stain is negative but suspicion of septic arthritis remains high, a regimen of both vancomycin and either ceftazidime or an aminoglycoside should be given [21]. If clinical suspicion for another organism not covered by this regimen is high such as Pseudomonas aeruginosa among injection drug users or N. gonorrhoeae in those at risk for sexually transmitted causes, additional therapy should be added accordingly. Once culture and susceptibility results become available, the antibiotic coverage should be narrowed appropriately.

The duration of therapy is variable and depends on the organism, severity of infection, and physician preference as there is limited data to inform this decision. Generally, gonococcal arthritis is treated for 7–14 days, and nongonococcal bacterial arthritis requires 2–4 weeks of parenteral antibiotics. Many physicians give an initial course of parenteral antibiotics followed by additional oral therapy. One study from the United Kingdom defined an adequate duration of intravenous treatment as at least 7 days in adults and an adequate oral duration as 14 days [22]. Retrospective review demonstrated a mean duration of therapy of 10.2 days with IV therapy and 55.3 days with oral therapy [22]. Others have recommended a minimum duration of treatment of 3 weeks for injections due to staphylococci and Gram-negative bacilli and at least 10–14 days for streptococci, meningococci, and Haemophilus but emphasize that these are minimums, and actual duration must be adjusted based on clinical response to therapy [23].

In addition to antibiotic treatment, drainage of the septic joint is typically performed. This may be done using arthrocentesis or surgery. If arthrocentesis is used, daily joint aspiration, particularly for the first 5 days of treatment, may be required. Synovial fluid should be analyzed to confirm an appropriate response to the selected treatment. Arthroscopic or open surgical techniques may also be utilized to rapidly drain the joint and debride any necrotic tissue that is present.