Sclerotic Sacro-iliac Joint

If you find a sclerotic sacro-iliac joint, look for the space of this joint if it is wide or obliterated.

1-If it is wide, think for sacro-iliitis.

2-If it is narrowed, think for

Ankylosing Spondylitis or Reiter’s Syndrome

Then look for spines searching syndesmophytes,If it is symmetrical think for ankylosing spondylitis. If it is asymmetrical think for Reiter's syndrome

Syndesmophytes are generally seen only in the seronegative spondyloarthropathies. These are due to inflammation and ossification of the outer fibers of the annulus fibrosus, known as the Sharpey's fibers.

Findings

The plain films

— demonstrate multiple

— asymmetric spinal

syndesmophytes.

There is bilateral

sacroiliitis and

— sacrospinous ligament

ossification in a case of Reiter's syndrome       

This patient

 presents with

sacroiliitis

There are

multiple

symmetric

fine

syndesmophytes

bridging squared

 vertebrae

There is anterior

 posterior, and

 interspinous

ligament

ossification in a case of  Ankylosing Spondylitis