Bilateral, simultaneous pneumococcal septic arthritis of the knees: a normal immune system, an unknown source.

Pneumococcal septic arthritis is a rare clinical entity and is often associated with a systemic bacteraemia. A 60-year-old man was admitted with bilateral swollen, painful knees. He was feeling feverish with raised inflammatory markers. Joint aspiration yielded purulent fluid, which, when cultured, grew Streptococcus Pneumoniae bilaterally. The patient underwent repeated arthroscopic knee washouts and was treated with intravenous (IV) antibiotics. During his admission, various investigations and scans were undertaken to find an infective focus or signs of immunodeficiency; none were found. After 4 weeks of IV antibiotics and 4 knee washouts, the patient was discharged. We believe this is the only case documented of bilateral simultaneous pneumococcal septic arthritis of the knees in an immunocompetent patient with no extra-articular infective focus. This case exemplifies the importance of careful assessment of patients who present with bilateral swollen joints.