Ankylosing spondylitis (AS) is a typical representative of SNSA. It is a chronic, systemic, inflammatory disease with an unknown etiology that mainly affects the mid-axis joints of the spine. It can involve the sacroiliac joints, spine and peripheral limb joints, eyes, heart, lungs and other organs, and is characterized by progressive fibrosis and ossification of tendons, ligaments, synovial membranes and osteophytes attached to the bone. The age of onset is usually between 15 and 30 years old, with fewer cases occurring after the age of 40; the incidence of relatives of patients is 20 to 30 times higher than the normal population, and about 96% of patients contain the serum histocompatibility antigen HLA-B27. The clinical manifestations of spondylitis are: (1) slow onset, early sensation of low back pain, inflexible lumbar activities, obvious in the morning, better after activity, and inflexible after sedentary activities. The symptoms get worse day by day. (2) The joint pain first appears in the sacroiliac joint, which may occur first on one side and then on the opposite side, or it may occur bilaterally at the same time. There is pressure pain at the sacroiliac joint, and the sacroiliac joint test is positive. (3) Low back pain below the spine and stiffness of the lower back with difficulty in movement are the early symptoms, and Shober Test (+) may appear on examination. When it gradually develops to the thoracic spine, such as when the rib spine joint is involved, there is dyspnea, band-like chest pain, and severe pain in the spine when coughing and sneezing. When it develops to the cervical spine, head rotation is not easy and the whole spine is completely stiff. Due to the stronger flexor muscles than extensor muscles and the patient’s posture of curling the trunk, the spine has a rounded hunchback deformity. (4) Some patients have unilateral or bilateral hip pain, and in the long run, the hip joint movement is restricted and flexion is tense.