Acute Klebsiella pneumoniae infection of the knee joint following anterior cruciate ligament reconstruction in a young adult: A case report

Acute postoperative infection caused by Klebsiella pneumoniae after anterior cruciate ligament reconstruction in young, immunocompetent individuals is exceedingly uncommon. An immunocompetent man in his early 20s developed fever and progressive swelling of the knee 5 days after anterior cruciate ligament reconstruction. Laboratory evaluation demonstrated markedly elevated inflammatory markers, including a C-reactive protein level of 18.36 mg/dL and synovial fluid white blood cell count of 62,667/mm 3 . Culture of aspirated synovial fluid confirmed infection with Klebsiella pneumoniae , establishing a diagnosis of acute postoperative septic arthritis of the knee. The patient underwent prompt arthroscopic debridement with biofilm debulking. Empirical intravenous piperacillin–tazobactam was administered for 3 days, followed by targeted intravenous levofloxacin for 5 days, and oral levofloxacin to complete an 8-week antimicrobial course. Infection was successfully controlled without graft or implant removal. The patient exhibited clinical improvement with resolution of fever and inflammatory signs following treatment. This case highlights that acute Klebsiella pneumoniae infection of the knee joint can occur even in young, immunocompetent patients shortly after anterior cruciate ligament reconstruction, without an identifiable remote infectious focus. Early recognition, prompt arthroscopic intervention, minimal implant burden, and appropriate targeted antibiotic therapy may enable successful infection control in selected patients.