Tuberculous arthropathy is a type of musculoskeletal manifestation of tuberculosis (TB) and a common cause of infectious arthritis in developing countries. Any pathological joint lesion where the exact diagnosis is equivocal should be considered tubercular in origin unless proven otherwise.
Please refer to the main article on tuberculosis for a general and broad discussion of this condition.
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Epidemiology
Although rare in western countries, tuberculous arthropathy is still a common problem in developing countries. Tubercular arthropathy is never a primary lesion, it is always a sequela of pulmonary or lymph node tuberculosis. It can occur at any age. There is no sex predilection for the disease.
Diagnosis
Initial acid-fast bacilli smears are often negative. Synovial culture is positive in ~80% of cases 6.
Pathology
The primary causative organism is Mycobacterium tuberculosis; however, atypical mycobacteria, i.e. Mycobacterium kansasii, M. xenopi and M. avium intracellulare, are also isolated in immunocompromised individuals.
The organism reaches the bone and remains dormant until recrudescence occurs. Any factor which modifies the state of local resistance and resultant activation of dormant tubercle bacilli, microtrauma has been proposed as a mechanism; however, trauma as an etiological factor has not been established.
Location
The most common form of articular tuberculosis is spondylitis followed by arthritis of weight-bearing joints (especially knee and hip 6). The spine is the most common site, followed by the hip joint, which constitutes approximately 15% of all cases.
Tubercular arthropathy can affect any joint but is frequently reported in the knee, ankle, sacroiliac joint, sternoclavicular joint, shoulder, elbow, and wrist. Tubercular arthropathy is usually monoarticular.
Several types of tuberculosis in the shoulder have been described and are discussed separately in the article shoulder tubercular arthropathy.
Radiographic features
Plain radiograph
Plain films are reliable for detecting tubercular arthropathy and for follow up of treatment. A triad of radiologic abnormalities (Phemister triad) includes:
peri-articular osteoporosis
peripherally located osseous erosion
gradual joint space narrowing
Tubercular arthropathy can be divided by radiological features into early and late stages:
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early stages (synovitis and arthritis)
periarticular demineralization
joint space widening (due to joint effusion)
mild subchondral erosion
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late stages (erosion and destruction)
gradual narrowing of joint space (there is involvement of articular cartilage)
severe subchondral erosion and destruction
pathological subluxation and dislocation
fibrous ankylosis - in contrast to pyogenic arthritis, the development of bone ankylosis is uncommon in tuberculous arthritis and, when present, is more likely to be secondary to prior surgical intervention
atrophic changes in bones may occur and lead to atrophic arthropathy (seen in shoulder joint as carries sicca)
Ultrasound
Joint effusion may be the only finding but is non-specific.
CT
CT can establish the degree of bone destruction or, rarely, sequestrum. Extension of infection into surroundings or any sinus tract formation can also be demonstrated on the post-contrast scan.
MRI
The lesions are typically:
T1: hyperintense
T2: hypointense
T1 C+ (Gd): brilliant enhancement
This may be a result of the presence of blood degradation products, inflammation, necrosis and fibrosis, which is seldom seen in other proliferative arthropathies.
MRI can assess associated abnormalities (e.g. osteomyelitis, myositis, cellulitis, periarticular abscess, tenosynovitis, bursitis, skin ulceration or sinus tract formation):
sinus tracts appear as a linear T2 hyperintensity with a marginal 'tram track' enhancement
periarticular abscesses have a thin, smooth, enhancing wall
Treatment and prognosis
A complete course of chemotherapy is the most important therapeutic approach. In advanced cases, surgical treatment is indicated if the deformity is limiting.
Differential diagnosis
Differential diagnosis of tubercular arthropathy may include causes of erosive arthritis, monoarticular arthropathy and arthropathies resulting in ankylosis and joint destruction, such as:
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synovial thickening is more uniform and bone erosions are much larger with defined rim enhancement in tuberculous arthritis
extra-articular cystic masses are more frequent and more numerous
symmetrical polyarticular distribution