Table 1.

The modified "New-York-Criteria" [1,5].

Clinical Criteria:
Lower back pain and stiffness for more than 3 months with improvement after exercise, but not with rest
Reduced motility of the lumbar spine in the sagittal and frontal axis
Restriction of the chest expansion (age and gender related)
Radiological Criteria:
Sacroiliitis at least grade 2 bilateral or grade 3–4 ipsilateral