Conventional radiography is a well established method for detecting permanent damage (structural changes) in the sacroiliac joints.

For all forms of spondyloarthropathy, the degree of severity is classified according to the New York criteria for ankylosing spondylitis in 5 stages.

• Grade 0: Normal findings.
• Grade 1: Suspicious changes.
• Grade 2: Minimal abnormality with small areas of erosions or sclerosis without alteration in the joint width.
• Grade 3: Unequivocal abnormality - moderate or advanced sacroiliitis consisting of erosion, sclerosis, widening, narrowing, and/or partial joint fusion (ankylosis).
• Grade 4: Severe abnormality in the form of total ankylosis.