Laboratory testing related to septic arthritis is important to identify the microorganism causing the infection, to determine which antimicrobial therapy will be effective, to monitor the effectiveness of treatment, and to evaluate the physical status of the affected joint(s).
- Synovial (joint) fluid analysis – to detect the presence of inflammatory cells or crystals that may indicate either an infectious or non-infectious cause (just as gout) for joint pain and symptoms
- Culture of joint fluid – to detect the presence of bacteria, mycobacteria, or yeast in the joint in order to determine the antimicrobials to which they are susceptible and to evaluate the effectiveness of treatment
- Blood culture – to determine if a microorganism is present in the blood
- Complete blood count (CBC) – to determine the presence and number of red and white blood cells that would indicate reaction to an infection in order to help evaluate and monitor the condition
- Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) – to detect inflammation; useful in following response to therapy
- X-ray of joint(s) – to help evaluate joint damage; may not show abnormalities until significant damage exists