An unusual case of primary tuberculosis of the patella and patellar tendon masquerading as gout

Abstract

Tuberculosis (TB), an infection caused by Mycobacterium tuberculosis, accounts for significant morbidity and mortality worldwide. While primary TB predominantly involves the respiratory system, approximately 10–19% patients have musculoskeletal involvement. We present a case of a 54-year-old year gentleman with insidious onset of anterior knee pain. Imaging demonstrated a soft tissue lesion involving the patellar tendon and eroding the inferior pole of the patella. The imaging features, particularly ultrasound, resembled those that are typically seen with gout. Ultrasound guided biopsy revealed this to be TB of the patella. The patient was successfully treated with antitubercular therapy. Musculoskeletal TB, while usually not a primary form of TB, is an important consideration particularly in patients with risk factors for the disease. Its imaging features can mimic other forms of arthropathy such as gout. Moreover, while the knee is a relatively common site for TB infection, isolated involvement of the patella and patellar tendon is extremely rare. The case highlights the possibility of rare musculoskeletal manifestation of TB as a well as a potential imaging pitfall of TB infection mimicking gout, which is an important consideration in clinical practice.