Knee Tuberculosis Masquerading as Pigmented Villonodular Synovitis: A Challenging Diagnostic Case Report

Osteoarticular tuberculosis is a symptom of extrapulmonary tuberculosis (EPTB) in around 10% of patients.[3] Tubercular arthritis usually manifests as a monoarticular disorder that affects weight-bearing joints such the knee, hip, and spine.This kind of arthritis is distinguished by its affinity for certain specific joints.[8] Tuberculous arthritis can be difficult to diagnose effectively, especially in young, immunocompetent individuals.This problem derives from the condition's rarity, unique clinical presentation, and vague radiological findings.[4] As a result, such individuals are frequently misdiagnosed and treated as having pyogenic arthritis, bone tumors, or other inflammatory conditions.[2,1] Knee tuberculous arthritis can mimic pigmented villonodular synovitis (PVNS), a benign proliferative illness affecting the bursa, tendon sheaths, and synovium that line the joints.[2]There are two forms of tuberculous arthritis: diffuse and localized.The diffuse type affects the whole tendon sheath, bursa, or synovial lining, whereas the localized form affects only a section of them.It is essential to treat any type of tuberculous arthritis as soon as possible to avoid significant cartilage damage and high-grade joint deformity.Delay in therapy might be damaging to joint health.[7]Furthermore, it is vital to recognize that the therapeutic techniques for tuberculous arthritis and pigmented villonodular synovitis (PVNS) are fundamentally different.Tuberculous arthritis is often treated with long-term antitubercular chemotherapy.In contrast, PVNS frequently demands synovectomy, which is the surgical removal of the afflicted synovial tissue.These diverse treatment approaches underscore the significance of correct diagnosis in order to give the most effective therapy for each ailment.[5] Differentiating between these two disease entities is critical for achieving the best possible patient outcomes.Histopathological analysis of the open biopsy revealed granulomatous inflammation consistent with chronic granulomatous disease (Figure 2).Additionally, Ziehl-Neelsen staining of the biopsy sample identified Acid-fast bacilli (Figure 3).These findings were pivotal in revising the diagnosis to tuberculous arthritis, rather than pigmented villonodular synovitis.