Joint pain with or without erythema and swelling is the most frequently encountered rheumatologic problem in the ED. A multitude of conditions can present as inflammatory arthritis, including septic arthritis, gout, pseudogout, and several autoimmune diseases such as RA, SLE, serum sickness, and sarcoidosis.
Among these, the one diagnosis that cannot be missed in the ED is septic arthritis. Failure to recognize infectious arthritis at initial presentation can result in significant morbidity and mortality. Therefore, the key question that the emergency provider needs to answer in the patient presenting with a nontraumatic painful joint is: “Does my patient have septic arthritis?”
Septic Elbow. Left elbow swelling and redness in a patient with septic arthritis. (Photo contributor: Lawrence B. Stack, MD.)
Unfortunately, very few clinical parameters are helpful when trying to differentiate infectious from other types of inflammatory arthritis. For example, fever, erythema, and limited range of motion are common in all types of inflammatory arthritis. Furthermore, serum parameters such as white blood cell count or C-reactive protein (CRP) are of limited value. A normal white blood cell count can be seen in 50% of patients with septic arthritis. CRP is elevated in most types of inflammatory arthritis but does not allow separation between septic and nonseptic etiologies.
Septic Elbow—Bony Erosion. Erosion of the proximal olecranon in a patient with septic arthritis. (Photo contributor: David Effron, MD.)
Septic Synovial Fluid. Purulent synovial fluid from a patient with septic arthritis. (Photo contributor: David Effron, MD.)
The most important diagnostic step in evaluating the patient with inflammatory arthritis is synovial fluid aspiration and analysis including cell count, crystal analysis, and Gram stain and culture.
Management and Disposition
If a patient is thought to have septic arthritis, immediate IV antibiotic treatment and timely orthopedic consultation are warranted. Of note, it is often not possible to confirm a diagnosis of septic arthritis in the ED with certainty, since synovial fluid cultures require time to grow and the Gram stain will be negative in the majority of cases. In general, inflammatory mono- or oligoarthritis should be treated as septic arthritis if no alternative etiology is found.
The antibiotic of choice is vancomycin, as it provides good gram-positive coverage, including methicillin-resistant Staphylococcus aureus. In patients with IV drug use or immunosuppression, gram-negative coverage such as third-generation cephalosporin should be added.
Septic Hip Joint Aspiration. Purulent synovial fluid aspirated from the hip of a child with a septic hip. (Photo contributor: Lawrence B. Stack, MD.)