Diagnostic Approach to Septic Arthritis

Key Evidence and Recommendations

• The Infectious Diseases Society of America recommends suspecting septic arthritis in patients with a sinus tract or persistent wound drainage over a joint, acute onset of a painful joint, or any chronic painful joint at any time after trauma or surgery 1
• Joint aspiration with synovial fluid analysis should be performed in all patients with suspected septic arthritis, regardless of CRP level, as recommended by the Infectious Diseases Society of America 1
• The diagnostic workup should include synovial fluid total cell count and differential leukocyte count, synovial fluid culture for aerobic and anaerobic organisms, and serum CRP and ESR as part of the initial evaluation, but not as sole determinants, according to the Infectious Diseases Society of America 1, 2
• The combination of abnormal ESR and CRP provides the best sensitivity and specificity, but should never be used alone to exclude infection, as stated by the Infectious Diseases Society of America and Praxis Medical Insights 1, 2
• For prosthetic joint infections, combining CRP, ESR, and fibrinogen improves accuracy, with abnormal results in at least 2 of 3 tests providing 93% sensitivity and 100% specificity, according to Praxis Medical Insights 2
• If antibiotics can be safely withheld, delay treatment for at least 2 weeks before joint aspiration to increase culture yield, as recommended by the Infectious Diseases Society of America 1
• CRP may be falsely reassuring in early infection, as it rises 12-24 hours after inflammatory insult and peaks at 48 hours, so early presentation may show normal values, as noted in Critical Care Medicine 3