A 50-year-old diabetic woman presented with painful swelling of the right knee and proximal part of the calf. A radiograph revealed gas shadows in the suprapatellar pouch and soft tissues of the posteromedial aspect of the proximal part of the calf. An arthrotomy was performed to evacuate pus and debride the synovium. The collection in the calf was approached through a separate posteromedial incision. Citrobacter freundii was isolated on culture, and the patient was given antibiotics to which it was sensitive.
The constellation of signs, symptoms, and radiographic features was characteristic of emphysematous septic arthritis. The patient recovered well following surgery and treatment with antibiotics. To our knowledge, this is the first reported case of such arthritis caused by C. freundii.