CRP and bacterial arthritis: The purpose of this study is: (1) to determine the failure rate of a single surgical incision and drainage (I&D) in pediatric septic arthritis, (2) to identify risk factors for failure which are detectable at the time of initial presentation, and (3) to trend post-operative C-reactive protein (CRP) values to see if there is a difference between children who fail a single I&D and those who do not.