Background: Tuberculous arthritis is not uncommon. The diagnosis can be challenging as the symptoms are insidious, concomitant signs of prior or active pulmonary disease is present only in fifty percent of cases, and the sensitivity of initial diagnostic studies are low.
Case Report: A 55 year old male with a history of alcoholic cirrhosis presented to our hospital with right knee pain and intermittent swelling for 15 months. The patient had been evaluated at two other hospital facilities and treated for presumed septic arthritis and osteomyelitis. On our initial evaluation, the patient had a swollen right knee and an arthrocentesis yielded purulent fluid. Cultures of the synovial fluid were negative. Synovial tissue stain and culture from an arthroscopy were positive for Mycobacterium Tuberculosis (MTb). In addition, the patient was diagnosed with pulmonary tuberculosis. He required repeat arthroscopy for a reaccumulating joint effusion, but eventually improved after nine months of antituberculous therapy.
Conclusions: Tuberculous arthritis should be considered in the differential diagnosis for chronic knee pain with effusion. The joint fluid characteristics vary widely and stains and culture of joint fluid have low sensitivity for mycobacterium tuberculosis. Synovial tissue cultures have the best sensitivity for diagnosis. Finally, although our patient was also diagnosed with pulmonary tuberculosis, concomitant signs of pulmonary tuberculosis are not always present.

Keywords: tuberculous arthritis, synovial fluid analysis, pulmonary disease