Clinical Manifestations. Tuberculous arthritis often involves only one joint. In order of frequency, the joints affected are the spine, hip, knee, elbow, ankle, sacroiliac, shoulder, and wrist. The onset of symptoms may be insidious. In children, the first symptom is often a limp or severe muscle spasm that occurs at night. Clinical examination reveals a “doughy” swelling (without erythema) of joints in the limbs, with fluid accumulation and early, severe, localized muscle atrophy. When the spine is involved (Pott disease), walking and negotiating steps are painful. Pott disease often causes anterior wedging of the vertebrae, resulting in an angular kyphosis that is evident on physical examination. Signs of spinal cord compression varying from reflex changes to paraplegia may occur. In late-stage infection, draining sinuses may develop around the affected area.

Radiographic Findings. Radiographs help to establish the diagnosis. The earliest observable change is the decalcification of bone near the diseased joint. Later, marked irregularity and narrowing of the cartilage space indicate subchondral bone invasion. Decreased density of cortical bone is evidence of regional atrophy of bone. In advanced disease, bone necrosis may be extensive, resulting in complete destruction of the joint architecture. Soft tissue shadows of abscesses may be evident.

Laboratory Studies. The tuberculin skin test (or an IFN-γ release assay) is usually strongly positive. In about 50% of patients, chest radiographs show pulmonary tuberculosis. Laboratory tests are usually needed to confirm the diagnosis.

Synovial fluid analysis often reveals a white blood cell count of more than 10,000/mm³ with a high content of mononuclear cells (neutrophils) in early infection. Examination of stained smears of synovial fluid seldom shows acid-fast bacilli, but culture of synovial tissue obtained via biopsy is usually positive.

Treatment. Prolonged chemotherapy is usually curative, even in advanced cases. Surgical drainage, synovectomy, or fusion may be required.