What are the new york criteria for AS?

Diagnosis (Clinical [low back pain and stiffness for more than 3 months improves with exercise not relieved by rest, limitation of spinal motion both saggital and frontal plane, and limitation of chest expansion relative to normal values] Radio [Sacroilitis grade >2 bilaterally/ grade 3-4 unilaterally]) Grading (definite dx if radio finding + 1 clinical, probable if three clinical , or radio alone)