Tuberculosis still ranks as one of the three most important infectious diseases in the world in terms of morbidity and mortality. In Korea, an increased incidence of tuberculosis has been observed in recent years. With the resurge of tuberculosis, extrapulmonary tuberculosis has increased, too. From this point of view, tuberculous arthritis affecting knee is rare in all forms of tuberculosis, but we can consider tuberculous arthritis in patients with osteomyelitis. We report the case of a 14-month-old male child who presented with fever and swelling on the left knee joint. Histologic examination of knee joint fluid showed consistent with tuberculosis. Ziehl-Neelsen stain of joint fluid was positive for acid-fast bacilli(AFB). The outcome was favorable after treatment with anti-tuberculosis medication. Because clinical signs and symptoms of musculoskeletal tuberculosis in children is more indolent, we can misdiagnose or delay diagnosis. The diagnosis of tuberculous arthritis can be elusive, necessitating a high index of suspicion.