Primary bone and joint tuberculosis

Primary bone and joint tuberculosis, also known as osteoarticular tuberculosis, is an extrapulmonary form of tuberculosis caused by infection with Mycobacterium tuberculosis that primarily affects the skeletal system without a preceding or concurrent pulmonary focus. This condition accounts for approximately 10-35% of extrapulmonary tuberculosis cases. The infection most commonly involves the spine (Pott's disease or spinal tuberculosis), followed by the hip and knee joints, though any bone or joint can be affected. The disease results from hematogenous spread of the mycobacterium to bone and joint tissues, where it causes chronic granulomatous inflammation leading to progressive destruction of bone and cartilage. Key symptoms include chronic, insidious pain in the affected bone or joint, swelling, stiffness, and reduced range of motion. In spinal tuberculosis, patients may develop kyphotic deformity (gibbus), paravertebral abscess, and in severe cases, neurological complications including paraplegia due to spinal cord compression. Constitutional symptoms such as low-grade fever, night sweats, weight loss, and fatigue may be present but are not always prominent. Cold abscesses (without the typical signs of acute inflammation) and sinus tract formation are characteristic features. Joint involvement typically presents as a monoarticular arthritis with gradual onset. Diagnosis relies on a combination of clinical suspicion, imaging (X-rays, MRI, CT scans), microbiological confirmation through culture or PCR of tissue or aspirate samples, and histopathological examination showing caseating granulomas. Treatment consists of prolonged anti-tuberculosis chemotherapy, typically involving a combination of first-line drugs (isoniazid, rifampicin, pyrazinamide, and ethambutol) for an initial intensive phase of 2 months followed by a continuation phase of at least 4-6 months, though many experts recommend extended treatment of 9-12 months for bone and joint involvement. Surgical intervention may be necessary in cases of spinal instability, significant neurological deficit, large abscesses requiring drainage, or failure to respond to medical therapy. Early diagnosis and treatment are essential to prevent permanent skeletal deformity and disability.

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