Confirmation of the diagnosis of ankylosing crestitis includes clinical and radiological criteria, and the more commonly used is the modified New York diagnostic criteria: (1) Clinical criteria ①Lumbar pain and stiffness for more than 3 months, with improvement in activity and no improvement at rest. (②Limited lumbar frontal and sagittal movement. (③) Thoracic mobility is lower than that of a normal person of corresponding age and sex. (2) Radiological criteria Bilateral sacroiliac arthritis at or above grade II or unilateral sacroiliac arthritis at grade III-IV. (3) Diagnosis ① Definite ankylosing crestitis meeting radiological criteria and 1 or more clinical criteria. (2) Possible ankylosing crestitis meeting clinical criteria without radiological criteria or meeting radiological criteria without any clinical criteria.