CASE REPORT Septic arthritis of knee masquerading as haemarthrosis in a patient on warfarin Senthil Nathan Sambandam * , Vijay Ramasamy, Murali Venkatesan, James Doyle Orthopaedics, 13, Blue Block, Fairfield General Hospital, Bury, UK Accepted 3 January 2006 Background Haemarthrosis in patients taking warfarin is a com- mon orthopaedic scenario. The diagnosis is usually clinical. Patients usually present with painful swel- ling of the knee. The differential diagnosis includes inflammatory arthritis and septic arthritis. The role of diagnostic aspiration of the knee is debatable. In the absence of constitutional symptoms and pre- sence of elevated INR, it is an accepted practice to treat the patient empirically on analgesics, bed rest and normalisation of INR, if the patient’s medical condition allows. We present an atypical case of septic arthritis of the knee masquerading as hae- marthrosis in a patient on warfarin. Case report A 56-year-old male presented to the Accident and Emergency department complaining of pain in his right knee. His pain was spontaneous in onset and had been present for 24 h. There was no history of trauma or illness. The patient correlated his pain and swelling to a DIY activity which involved bending his knee. He had a medical history of valvular heart disease for which he was prescribed warfarin. On examination, the patient was apyrexial (36.8). The knee was warm, tender and swollen with a grade II effusion. His white cell count was 7300/mm 3 , CRP was 4 units and his INR was 1.8. A provisional clinical diagnosis of haemarthrosis was reached based on these findings and the patient was treated with analgesia and bedrest. Despite normalising the INR, the patient’s pain and swelling increased. A decision to aspirate the knee was made. Sixty milli- litres of yellow coloured fluid was aspirated and sent for microscopy and culture and sensitivity. The aspirate grew Staphylococcus aureus. The patient was taken to theatre for arthroscopic washout of his knee joint and antibiotics (Flucloxacillin 500 mg qds) was commenced. The patient made a full and uneventful recovery. Discussion This is an interesting case not only because the presentation was atypical but also because this incident raises an argument for routine aspiration of all cases of suspected knee haemarthrosis in patients taking warfarin. Haemarthrosis of the knee in patients on warfarin therapy is a very common clinical condition. Haemarthrosis can be treated in Injury Extra (2006) 37, 272—273 www.elsevier.com/locate/inext * Corresponding author. Tel.: +44 7969684248/1617782330. E-mail address: sam_senthil2002@yahoo.co.in (S.N. Sambandam). 1572-3461/$ — see front matter # 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.injury.2006.01.013