I’ve had back and sacroiliac joint pain off and on for the last six months. The doctors finally diagnosed it as ankylosing spondylitis. They want to do MRIs to see what’s going on in the low back area. What do MRIs show that you can’t see on an X-ray?

Ankylosing spondylitis (AS) is a chronic, painful, inflammatory arthritis that mainly affects the spine and sacroiliac joints (SIJs). It eventually causes the sacroiliac joints and spine to fuse.

X-rays show changes in the bones and joints but not until the disease has progresses. It can be up to 10 years after the start of the disease that changes are seen on the X-ray. By that time, it may be too late to change the pattern.

On the other hand, MRIs offer early clues to subtle changes in the spine and sacroiliac joints. For example, active inflammation of the sacroiliac joint called sacroiliitis is apparent with an MRI scan. Signs of sclerosis (hardening of the bone around the joint) will tip the physician off to progressive changes occurring in the sacroiliac joints and spine.

Early diagnosis and prompt treatment are essential to minimizing the damage that can occur with this condition. Controlling signs and symptoms for as long as possible is the key to maintaining spinal mobility, physical movement, and function. Type of treatment (medications, physical therapy) and aggressiveness of therapy can be aided by the information provided by all diagnostic tests (lab values, X-rays, MRIs).