New York modified criteria (1984) for ankylosing spondylitis*
| (1) Low back pain with inflammatory characteristics |
| (2) Limitation of lumbar spine motion in sagittal and frontal planes |
| (3) Decreased chest expansion |
| (4) Bilateral sacroiliitis grade 2 or higher |
| (5) Unilateral sacroiliitis grade 3 or higher |
| *Definite AS when the fourth or fifth criterion mentioned presents with any clinical criteria |