Septic Arthritis

After a physical exam of your joint, if your healthcare provider suspects you have septic arthritis, they will most likely withdraw synovial fluid (the fluid that lubricates your joint) from your affected joint with a needle. This is called aspiration. They will then do a laboratory test to look at the synovial fluid. Having bacteria in the synovial fluid of your joint confirms the diagnosis of septic arthritis.

What tests are used to diagnose septic arthritis?

Tests that are used to diagnose septic arthritis include:

• Synovial fluid aspiration: Your healthcare provider may withdraw fluid from your affected joint with a fine needle to check it for bacteria. This is known as aspiration.
• Blood tests: Your provider may have you undergo blood tests to see if your body’s immune system is responding to an infection and/or to rule out other possible issues.
• X-rays: X-rays use radiation to take images of your bones. X-rays can show widened joint spaces and bulging of the soft tissues, which can be signs of septic arthritis.
• Ultrasound: Ultrasound uses sound waves to take pictures inside your body. An ultrasound can help your provider see how swollen your joint is and help them see your joint fluid when aspirating it.
• MRI: An MRI (magnetic resonance imaging) uses a large magnet, radio waves and a computer to make detailed images of your organs and bones. An MRI can help detect early cases of septic arthritis.