Indicators for detection of septic arthritis in the acutely swollen joint cohort of those without joint prostheses

Differentiating septic arthritis from culture-negative, acute atraumatic joint effusion is difficult. Studies have attempted to elucidate factors that herald infection, but, due to overlap, most conclude that the diagnosis ultimately relies on clinical judgment. Furthermore, studies are limited by broad inclusion criteria. The current retrospective case study sought to examine (1) which markers differentiate a culture-positive septic joint from culture-negative effusion in patients suspicious for infection despite no growth on Gram stain and without previous surgery in the affected joint and (2) whether threshold values of these markers exist that predict septic arthritis. The study was performed by reviewing records of those who underwent operative irrigation and debridement involving the shoulder, elbow, wrist, hip, knee, and ankle. Patients were included if they were older than 18 years and had an acutely swollen/painful joint and no organisms on initial Gram stain. Exclusion criteria were lack of serum markers or synovial fluid aspirate, antibiotics within 1 week, adjacent wound or skin infection, recent trauma to the joint, and previous joint infection or surgery to the joint. Several clinical, serological, and synovial parameters were collected and analyzed using paired t test with Bonferonni correction. Serum C-reactive protein was the only significantly different variable between groups. Serum C-reactive protein greater than 10.5 mg/dL was predictive of infection. In those suspicious for infection despite no growth on Gram stain and without previous surgery in the affected joint, C-reactive protein greater than 10.5 mg/dL is suspicious for joint sepsis and should warrant consideration for urgent irrigation and debridement.