A Novel Case of Citrobacter koseri Septic Arthritis in a Native Knee Joint

<i>Citrobacter koseri</i> is a rare cause of septic arthritis in a native knee joint. We present the first recorded case of <i>C. koseri</i> septic arthritis in the native knee from a hematogenous spread resulting from a gastrointestinal illness, along with a review of the literature. A search of PubMed, Embase, OVID, and Google Scholar was conducted. Fifteen cases of musculoskeletal infection were identified, and of these, only six cases involved a septic joint and one case involved a septic knee. None of the recorded adult cases presented hematogenously without prior trauma. All of the cases achieved resolution after either antibiotic treatment alone or in conjunction with surgical treatment. <i>Citrobacter koseri</i> is not a rare cause of infection in general. However, it is not a common cause of septic arthritis, and this may complicate the treatment course as it can be overlooked as a cause of infection. It is essential to obtain a thorough history and a broad differential diagnosis when evaluating septic arthritis as although it may be difficult to identify the infection, <i>C. koseri</i> septic arthritis can be effectively treated with surgery as well as newer generation beta-lactams and cephalosporin antibiotic therapy.