Sacroiliitis grading can be achieved using plain films according to the New York criteria 4.
- grade 0: normal
- grade I: some blurring of the joint margins - suspicious
- grade II: minimal sclerosis with some erosion
- grade III:
- definite sclerosis on both sides of joint 5
- severe erosions with widening of joint space with or without ankylosis
- grade IV: complete ankylosis