What should be performed on a swollen joint to rule out septic arthritis?

Aspirating the joint is a critical first step in evaluating a swollen joint to rule out septic arthritis. This procedure allows for the collection of synovial fluid, which can then be analyzed for the presence of infection. The fluid can be tested for white blood cell count, which is typically elevated in cases of septic arthritis, and can be cultured to identify any bacterial pathogens that may be responsible for the infection. Additionally, the appearance of the fluid can provide important diagnostic clues; for instance, cloudy or purulent fluid is often indicative of infection.

Furthermore, the timing of the aspiration is also important, as it should be done promptly to avoid potential complications from a septic joint, such as joint destruction or systemic infection. Other options, such as applying ice and rest, initiating antibiotics, or ordering an MRI, do not provide the necessary immediate diagnostic information to clarify whether septic arthritis is present. Ice and rest may manage symptoms but do not address the underlying cause. Starting antibiotics without confirmation of infection can lead to complications and altered culture results, while MRIs, although useful for further evaluation, are not immediate interventions and do not replace joint aspiration in the diagnostic process.