Diagnosis

During the physical exam, your doctor might ask you to bend in different directions to test the range of motion in your spine. He or she might try to reproduce your pain by pressing on specific portions of your pelvis or by moving your legs into a particular position. Also, your doctor might ask you to take a deep breath to see if you have difficulty expanding your chest.

Imaging tests

X-rays allow your doctor to check for changes in your joints and bones, though the visible signs of ankylosing spondylitis might not be evident early in the disease.

An MRI uses radio waves and a strong magnetic field to provide more-detailed images of bones and soft tissues. MRI scans can reveal evidence of ankylosing spondylitis earlier in the disease process, but are much more expensive.

Lab tests

There are no specific lab tests to identify ankylosing spondylitis. Certain blood tests can check for markers of inflammation, but inflammation can be caused by many different health problems.

Your blood can be tested for the HLA-B27 gene. But most people who have that gene don't have ankylosing spondylitis and you can have the disease without having the gene.