Pediatric bone and joint tuberculosis has decreased significantly in recent years and is a local manifestation of systemic tuberculosis infection, mainly due to hematogenous dissemination of Mycobacterium tuberculosis, which may explain why multiple bone and joint tuberculosis is common in pediatric patients. In addition, lymphogenic dissemination is also possible. Mycobacterium tuberculosis invades the bone ends (epiphysis, metaphysis) or synovial membrane via the blood or lymphatic circulation. The most common site of pediatric bone and joint tuberculosis is the spine, followed by the hip and knee joints, short bones and long bones. Trauma can turn occult bone tuberculosis lesions into active bone tuberculosis. The incidence of tuberculosis is higher in the limbs or joints with heavy load or movement, such as spinal tuberculosis is most common in children who can stand and walk, and the heaviest load in the thoracolumbar region is most likely to develop tuberculosis. Lower limb tuberculosis is more common than upper limb tuberculosis. Pathological changes] The pathological changes are most likely to occur in cancellous or spongy bone, which may be related to the rich vascular network there. For example, vertebral tuberculosis mostly starts in the central part of the vertebral body, long bone tuberculosis mostly starts in the epiphysis and metaphysis, and short bones often appear as central osteitis. These lesions are prone to caseous changes and can develop cold abscesses, sometimes at sites distant from the lesion. The nodular lesions may be limited to the bone and are simple bone tuberculosis, but are less common, with the elbow joint being the most common. The lesion may also begin in the synovium, which is called simple synovial tuberculosis, and is also rare. Simple synovial tuberculosis is more common in the knee, followed by the ankle and hip. Simple bone tuberculosis or simple synovial tuberculosis will develop into total joint tuberculosis within a few months or years if left untreated. Clinical manifestations] The course of the disease can be divided into three stages according to different stages of lesion development, such as the initial stage, the extreme stage and the quiescent stage, and the symptoms of each stage are as follows. The symptoms of tuberculosis poisoning include slight fever, loss of appetite, fatigue, lethargy, lack of energy and night sweats. The following signs can be seen locally: (1) Reflex muscle spasm: The muscles are in reflex spasm to protect the diseased spine or joints and limit their activities to reduce pain. The muscles are tense at this time. Children have night terrors or night cries, i.e., they suddenly wake up crying in pain during sleep at night, because the protective spasm disappears after sleep and causes pain when the spine or joints move. Due to the muscle spasm, the joint movement is restricted and it shows various bad postures. (2) Joint dysfunction: walking fatigue, uneven gait, clumsy and unstable gait, easy to fall, sometimes limping. (3) Pain: Initially, the pain is mild and disappears after rest, but later it is persistent. In addition to local pain, there is also radiating pain. (4) Muscle atrophy: initially due to neurotropic disorder, and later related to limb disuse. First, muscle tension is reduced compared to the healthy side, muscle strength is weakened, and then muscle atrophy and weakness. In addition, the subcutaneous fat layer of the affected limb, especially near the affected joint, is thickened. (5) Local swelling: the epidermal temperature is increased, and there may be percussion pain, pressure pain and joint effusion. There is a kneading sensation on palpation when the synovial membrane is thickened. Affiliated lymph nodes may increase in size. 2.Extreme stage At this time, the destructive lesions are dominant, and the general toxic symptoms are obvious. Local symptoms increase, deformity and limb shortening appear. In severe cases, joint dislocation and pathological fracture may occur. The cold abscess breaks down to the outside and forms a fistula, which may not heal for a long time. The paravertebral abscess of thoracic spinal tuberculosis may penetrate into the thoracic cavity or lung, causing pleural and pulmonary comorbidities such as abscess chest, limited pleurisy, paravertebral abscess-bronchial fistula and bronchial dissemination. 3.The quiescent period (repair period) activity basically disappears, and the regenerative process of the organism prevails. At this time, the general condition improves, toxic symptoms disappear, local symptoms such as pain, spasm and swelling disappear, and the fistula heals, but the deformity is permanently present. What is seen on X-ray: X-ray abnormalities are found about 3 months to 1 year later than clinical symptoms. Initially, there may be osteoporosis, decalcification, disturbance of bone trabeculae, blurred joint images, and narrowing of the joint cavity. The soft tissue around the joint is swollen. In the extreme stage, the joint cavity is narrowed or disappears, and the surrounding soft tissue shadow is widened. Extensive bone decalcification, bone destruction and defects, cavity formation and dead bone occur. Erosion of the epiphysis may cause dislocation of the joint. In the resting phase, the bone ends are clearly imaged, and the edges of the lesion are dense with bone, and osteophytes are visible. Abscess resorption or calcification may be seen. The joint may heal fibrously, or bony. Sometimes cavities and dead bone may persist for a long time.