Chronic knee swelling reveals a serious infection

In 2012, an 84-year-old Chinese man presented with progressive, chronic left atraumatic knee pain and swelling. 

His medical history was notable for pulmonary tuberculosis treated in China in 1951 and rheumatoid arthritis diagnosed in 2006. His joint pain progressed despite use of disease-modifying drugs and steroid injections. 

Antitumour necrosis factor inhibitors were not used because of concerns of tuberculosis reactivation.

Initial examination and treatment
Clinical examination showed