Tuberculous monoarthritis of the knee joint

A 47-year-old man presented to the emergency department with 2 weeks of acute-on-chronic pain in his right knee. When examined, the patient was afebrile with normal vital signs. His right knee was swollen with limited flexion and extension. He did not have any overlying erythema or tenderness to palpation of the bursa or the joint line. The patient was admitted to the internal medicine service and the initial treating physicians were concerned that he may have had a malignant disease; they ordered a CT scan of the chest, abdomen and pelvis, which showed mild, biapical lung scarring. At follow-up after the 9-month course of treatment, the patient had considerable improvement of his knee pain (pain only with extended use), periarticular and lower leg swelling and range of motion (full flexion and extension). He had returned to work and was ambulating without need for a mobility aid. However, he was lost to follow-up, and subsequent knee imaging and surgical referral could not be completed.