Musculoskeletal TB represents 1-3% of all tuberculous infections. It often has a nonspecific, gradual course leading to delayed diagnosis. Clinical presentations of musculoskeletal TB include painful or swollen joints or back pain along with constitutional symptoms like night sweats, loss of appetite and weight loss. Bone involvement is usually seen clinically 6 months to 3 years after the primary infection and is usually a result of hematogenous spread of the primary infection. However, absence of pulmonary TB does not exclude tuberculosis as the cause of osseous infection. 

TB could possibly affect any bone, joint or bursa. The hip and knee joints are commonly affected, with the sacroiliac joints, shoulders, elbows and ankles being affected less frequently, in that order. The femur, tibia and small bones of the hand and feet are most involved by tuberculous osteomyelitis, with the ribs also being frequently involved. The most common sites of bursitis are the trochanteric, subacromial, subgluteal and radioulnar parts of the wrist [1]. 

The following discussion will present specific characteristics associated with tuberculous involvement in a few common skeletal locations, with illustrative cases. 

1. TB shoulder 

The incidence of shoulder tuberculous arthropathy ranges from 0.9% to 1.7% [2,3]. Males are more likely to have this condition, and the left shoulder joint is frequently affected, as opposed to the pulmonary apical lesion the right side is more common [2,3].  

During the initial phase, imaging results display decreased bone density, effusion-induced joint space enlargement, and bone degradation beneath the cartilage [4].  Late-stage imaging may reveal sub-chondral bone abnormalities and bone degeneration, along with narrowing of the joint space that could result in subluxation or dislocation [3]. Ultrasonography may reveal soft tissue abscesses, increased vascularity, synovial fluid, and homogeneous thickening of the synovial membrane without nodules [4,5]. 

Fig 1: TB Shoulder: A 29-year-old female with chronic left shoulder pain. A) Left shoulder radiograph shows multiple boy erosions in the humeral head (blue arrows). MRI left shoulder B) Coronal PD fat sat, C) Coronal T2 & D) Coronal T1 post Gadolinium shows moderate to severe joint effusion with synovitis (red arrows). Differentials include granulomatous disease. Aspiration biopsy confirmed tuberculosis.

2. TB elbow 

TB elbow is known to occur in 2–5% of all bone regions [5,6]. TB of the elbow is characterized by discomfort, edema, and a progressive loss of joint range of motion [7]. The Phemister's trio of peri-articular osteoporosis, osseous erosions, and progressive joint space narrowing are non-specific radiographic alterations associated with tuberculosis infection [8]. MRI is useful mainly in earlier presentations when plain radiographs are nonspecific. Joint effusion and bone marrow changes appear hyperintense on T2-weighted images and hypointense on T1-weighted images. Synovial thickening, internal debris, loose bodies, calcifications and septations are hypointense on T2 weighted image [7]. 

Fig 2: TB Elbow: A 40-year-old male with left elbow tenderness and swelling. MRI left elbow T1 post Gadolinium A) Coronal & B) Axial in 2014 and C) Coronal & D) Axial in 2015 show mild elbow joint effusion with synovitis (red arrows), cold abscess (blue arrow) in the supinator muscle with myositis and erosion in the proximal ulna (yellow arrows). Patient had ultrasound guided biopsy. TB arthritis was confirmed. Patient lost follow up and after one year presented with pulmonary tb with increased bony erosion in the ulna. He was started on ATT and improved.

3. TB hand and wrist 

The indicators of TB in the hand include osteomyelitis in the metacarpals, phalanges, and tiny bones (carpal bones), or dactylitis [9,10]. The most prevalent kind of hand TB is tenosynovitis [11]. Anti-tuberculosis medication treatment may be necessary in conjunction with early diagnosis, surgical transection of the transverse carpal ligament, debridement, and total excision of the diseased synovium [9].  

Wrist TB can show a variety of X-ray abnormalities, such as bone cysts, osteolytic lesions (which are frequently encircled by sclerotic edges), reactive sclerosis, localized osteoporosis, joint destruction, and periosteal reaction, which might weaken a child's epiphysis [11]. MRI findings such as synovial thickening around the flexor and extensor tendons and synovial fluid collection with small hypointense nonenhanced foci in the tendon sheath are highly suggestive. Bone erosion, osteomyelitis, and median nerve encasement may also be seen [12]. 

Fig 3: TB Hand: A 40-year-old male with left hand pain. A) Left hand radiograph AP view shows expansile lesion of the middle phalanx (red arrow). MRI left hand coronal T1 B) pre contrast & C) post gadolinium shows destructive bony lesion in the proximal interphalangeal joint of the little finger (blue arrow) with surrounding soft tissue oedema, the proximal part of the middle phalanx shows multiple small lobulated destructive bony lesions (yellow arrow), distal part of the proximal phalanx is also involved with destruction of the joint. These findings are suggestive of tuberculosis dactylitis.

4. Chest Wall TB 

Apart from tubercular osteomyelitis of the rib, TB may also involve sternum, costochondral junctions, costovertebral joints and the vertebrae. X-rays are usually insensitive unless there is extensive bony destruction. Tuberculous sternal osteomyelitis mostly presents as bone loss on CT and X-ray however sclerosis may be rarely present. The radiographic and CT scan features of rib TB are bone erosions and destruction and adjacent abscess formation. MRI may also be helpful to detect bone and bone marrow changes.[13] 

Fig 4: TB Chest Wall: A 37-year-old male with sensory deficit and paraparesis. A) & B) CT Thorax with intravenous contrast bone window shows lytic lesion in the transverse process of D4 (red arrow) and adjacent ribs D4 (blue arrows) and D5 (yellow arrows). C) & D) MRI thorax with intravenous contrast T1 shows post contrast enhancement of the lesion along with neural spine with soft tissue component extending to the epidural space compressing the spinal cord (green arrow). Findings are suggestive of an infective etiology likely tuberculosis. Image guided biopsy proven TB.

5. TB of sacroiliac (SI) joint    

 TB of the SI joint typically presents with low back pain, hip pain, or difficulty walking, often accompanied by systemic symptoms like fever and weight loss. On MRI, multiple lesions with paravertebral abscess with asymmetrical SI joints involvement is virtually diagnostic. TB affects the sacroiliac joint through hematogenous spread from a primary focus but can also be due to direct extension from adjacent structures. Treatment typically involves long-term anti-TB therapy, and surgical intervention may be required in severe cases [14].  

Fig 5: TB of SI Joint: A 40-year-old male presented with low back pain. CT bone window A) Coronal pelvis, B) Axial thorax, MRI T1 post Gadolinium C) & D) Coronal and E) Axial cuts shows asymmetrical right sided sacroiliitis with mild bony destruction (red arrows) and destruction at the level of T11 body anteriorly with small paravertebral abscess with surrounding soft tissue enhancement at T11 on the left side (blue arrows)

6. TB hip  

Spondylitis is the earliest stage of joint TB, with the later stages including arthritis of the weight-bearing joints such as the knee and the hip [15]. In reverse order, the spine is the primary site with the hip contributing close to 15% of the occurrences. When an MRI is performed, the lesions appear as hyperintense in T1, hypointense in T2 and intense in T1 C+ (Gd) due to the presence of blood degradation products, inflammation, necrosis, and fibrosis, which are not common features associated with other interstitial osteoarthritis. MRI can also reveal other abnormalities such as osteomyelitis and the presence of abscesses or sinuses. 

Fig 6: TB Hip: A 40-year-old male presented with bilateral hip pain. A) Pelvis radiograph AP view shows subtle lytic lesion in the right femoral neck (green arrow). MRI pelvis B) Coronal T1, C) STIR & D) Coronal T1 post Gadolinium shows low signal intensity in T1 weighted images and bright on STIR involving the right femoral head up to its intertrochanteric area (red arrows). Right hip joint fluid with synovitis (blue arrows) and adjacent femoral head bony erosion. Multiple cold abscesses formation more evident subcutaneously adjacent to the gluteus medius extending down to the vastus lateralis muscle (yellow arrows). Image guided biopsy proved tuberculosis.

7. TB knee 

TB of the knee joint (gonitis TB) is the second most common form of skeletal TB after spinal TB, accounting for over 10% of cases [16-17].It presents as monoarthritis, typically affecting one joint, and progresses chronically, potentially leading to abscesses and fistulas if untreated [18]. 

Gonitis TB affects all ages but is more common in children and adolescents. It spreads hematogenously to synovial or subchondral areas (e.g., distal femur, proximal tibia, or patella). In adults, it can originate from epiphyseal bone, while in children, it often starts in the metaphysis, causing joint erosion and arthritis [19-20]. 

Fig 7: TB Knee: A 37-year-old lady with left knee pain. A) AP knee radiograph & B) CT coronal bone window shows erosive changes are seen in the lower end of femur and tibia (red arrows) with subarticular mild sclerotic changes, loss of joint space and decreased bone density. C) Gadolinium enhanced MRI coronal T1 demonstrates multiple small abscesses (yellow arrows) with erosions and surrounding enhancement.

8. TB ankle 

Osteoarticular TB rarely affects the ankle or foot, but when it does, it can mimic conditions like septic osteomyelitis, inflammatory arthritis, Charcot arthropathy, or tumors. TB arthritis is typically "cold," with no erythema or temperature change in the skin. Symptoms include pain, swelling, limited motion, bone tenderness, limping, and muscle spasms, often with systemic signs like fever and weight loss. X-rays reveal bone loss, erosions, and reduced joint space, while MRI helps define bone and soft tissue involvement. Early diagnosis is crucial to prevent joint degeneration and functional disability [21].

Fig 8: TB Ankle: A 38-year-old male, known case of pulmonary TB with left ankle pain. MRI left ankle A) Coronal PD, B) Coronal T1 post Gadolinium & C) Sagittal T1 pre contrast & D) Sagittal T1 post Gadolinium shows multiple well-defined destructive lesions at lower end of the fibula, the medial aspect the tibia and adjacent talus in the ankle joint (arrows), with post contrast peripheral enhancement of the lesions. The tibio-talar joint space is decreased with significant bony edema in the talus and adjacent tibia.