Introduction 

Tuberculosis (TB) remains a major global health burden, with extrapulmonary involvement in up to 20% of cases. Osteoarticular TB is rare (<3%) but poses significant diagnostic challenges because of its indolent, non-specific presentation. Chronic monoarthritis of the knee can be misleading, often leading to delayed diagnosis and irreversible joint damage.

Methods

We report a clinical case of chronic knee monoarthritis managed at a tertiary centre, including clinical, imaging, surgical, and microbiological findings, together with functional outcomes

Results

37-year-old patient admitted to the hospital due to hemoptysis Prior medical history: 4-month history of progressive knee pain, swelling, and functional limitation.

Tuberculosis diagnosed and MRI revealed a large, multiloculated, cystic lesion (23x9x8 cm), extending from the distal thigh to the proximal leg, communicating with the joint and consistent with a massive cold abscess. The popliteal artery was encased by the lesion, and the posterior tibial artery showed reduced calibre.

Fig. 1 & 2: MRI images demonstrating a large abscess posterior to the knee. T2-weighted and T1-weighted sequences, respectively.

Surgical debridement with neurovascular dissection and drainage of purulent material (400 mL). Microbiological analysis confirmed Mycobacterium tuberculosis.

Fig. 3: Post op after drainage and neurovascular bundle isolation.

Infection control was achieved with combined surgical and antituberculous therapy. Despite clinical improvement, the patient developed persistent functional limitation, including residual stiffness and secondary osteoarthritis. No signs of recurrence at 2 years of follow-up.

Conclusions

Tuberculous arthritis should be suspected in chronic monoarthritis, even without systemic symptoms. A cold abscess is an important diagnostic clue and may indicate advanced disease. Delayed diagnosis can result in extensive joint destruction and functional sequelae, highlighting the importance of early recognition and multidisciplinary management.