Clinical criteria:
(1) low back pain and stiffness for more than 3 months which is not relieved by rest.
(2) pain and stiffness in the thoracic region.
(3) limited motion in the lumbar spine
(4) limited chest expansion
(5) history or evidence of iritis or its sequelae
Radiographic examination of the sacroiliac joints
(1) look for evidence of sacroiliitis.
(2) exclude bilateral osteoarthritis.
Ankylosing spondylitis is present if:
(1) bilateral sacroiliitis is present, AND 1 or more clinical criteria are present.
(2) >= 4 clinical criteria are present.
where:
• The presence of bilateral sacroiliitis is considered the most important criterion for the diagnosis of ankylosing spondylitis.
