Bilateral native knee septic arthritis caused by group G Streptococcus: A rare presentation in an uncommon host

Background: Septic arthritis is an uncommon but severe condition that can lead to rapidly progressive articular destruction and septicemia. Although the knee is the most commonly affected joint in septic arthritis, bilateral involvement is an exceedingly rare condition often associated with immunocompromising conditions, medical comorbidities or other sources of infection. Case report: A 74-year-old male immunocompetent patient presented with two to three days of atraumatic bilateral knee pain and swelling with difficulty ambulating, with presenting vital signs concerning for sepsis. Physical exam was notable for large bilateral knee effusions, warmth and significantly limited range of motion. Bilateral knee arthrocentesis was performed with synovial fluid analysis consistent with bilateral septic arthritis. The patient was managed with intravenous antibiotics and operative arthrotomy and irrigation. Synovial fluid cultures from the emergency department and operating room, as well as 4/4 blood cultures all grew Group G streptococcus. No primary source of infection was identified. The patient completed a course of intravenous antibiotics tailored to culture susceptibility and had resolution of symptoms. Why should an emergency physician be aware of this?: Polyarticular septic arthritis carries high morbidity and mortality. Although uncommon, atypical presentations and absence of usual risk factors can lead to delays or missed diagnoses in the emergency department. It is essential to maintain a high index of suspicion in the patient presenting with undifferentiated multifocal joint pain or swelling, in the appropriate clinical context, to make an early diagnosis and initiate aggressive treatment to prevent complications.