Septic arthritis is a painful joint infection that needs quick treatment, often requiring surgery to clean the joint. Currently, doctors use a synovial fluid culture, a test on the joint fluid, to find infections. This test can take days, which might delay treatment. This study is exploring if certain proteins in joint fluid, like alpha-defensin, can quickly identify infections in children under 18. Alpha-defensin and other biomarkers are substances that might indicate an infection. For the study, doctors will take joint fluid from patients suspected of having an infection and compare it to fluid from patients without infections, using various tests including blood tests and stains to look for bacteria.

• Only one visit is required for the study.
• Joint fluid is needed, which is a standard procedure.
• Patients should not have had a major joint injury recently.

The aim is to improve how quickly doctors can detect infection, helping them decide if surgery is needed sooner. This could protect children’s joints from damage. If your child is suspected of having a joint infection, they may be eligible to participate.