A 53-year old woman presented to us because of pain and swelling of the right knee joint for the previous 2 days before admission. She took non-steroidal anti-inflammatory medication but experienced only minimal and temporary relief for a few hours. The pain and swelling got gradually worse. She checked her temperature and it was 400 C. The day before admission while the symptoms of the knee joint persisted, edema and pain appeared in the upper half of the calf musculature. The past medical history was significant for partial resection of the larynx due to idiopathic paralysis and a thyroidectomy for goitre.
Physical examination on admission showed a temperature of 38,50 C, blood pressure was 140/80 mmHg, respirations 14 per minute and pulse: 90 per minute regular. A tracheostomy was evident. The right knee had signs of inflammation: pain, redness, and edema. There was accompanying edema and pain of the calf musculature. The rest of the physical examination was normal.
Laboratory tests showed a leukocytosis with a shift to the left (15.250 leukocytes/mm3 with 80,9% neutrophils) and a markedly increased C-reactive protein (28,84mg/dl (normal: 0-0.5 mg/dl) and erythrocyte sedimentation rate (120 mm/1st hour (normal:0-20 mm/1st hour). Magnetic resonance imaging (MRI) of the right knee and the right calf (figure 1) disclosed extensive synovitis of the right knee with the concomitant presence of increased arthritic fluid. There was accompanying inflammation of the muscle groups of the calf and especially the gastrocnemius muscle and compression of the popliteal vein in the popliteal fossa.
What was the cause of fever, knee pain, and calf swelling?