To examine the involvement of the spine and sacroiliac joints in spondyloarthropathies using a multimodal radiologic approach (radiography, CT, MRI), providing a practical guide for the differential diagnosis of these conditions.

The inflammatory involvement of the spine and sacroiliac joints is the most peculiar featureof seronegative spondyloarthropathies (SpA), which include ankylosing spondylitis, psoriatic spondyloarthritis, reactive spondyloarthritis (Reiter's syndrome), enteropathic spondyloarthritis (related to inflammatory bowel diseases such as Crohn's disease and ulcerative colitis), undifferentiated spondyloarthropathies and SAPHO syndrome. The main clinical manifestations of SpA include inflammatory back pain caused by sacroiliitis or inflammatory involvement of the lumbar and/or distal thoracic spine; peripheral arthritis (often oligoarticular and asymmetric); enthesitis and extraskeletal manifestations, such as uveitis. In SpA, the...

Ankylosing spondylitis Sacroiliitis is the earliest alteration, followed by the involvement of the dorsal-lumbar spine.The involvement of the cervical spine is almost always late, and it can occur even 20 years ormore after the disease’s onset. Sacroiliitis affects both the synovial (antero-inferior) and the ligamentous (postero-superior) aspects of the joint, presenting, in most cases, a bilateral and symmetric distribution. In the early stages alterations are represented by juxta-articular osteoporosis, superficial erosions and progressive subchondral osteosclerosis, which is first focal, then more and more extended (Fig....

Bone marrow oedema, osteo-proliferative changes, erosions and osteo-sclerosis are the mainradiological findings of SpA, and multimodal imaging allows a complete demonstration of theinflammatory lesions in their different stages of progression. The diagnosis of SpA and theirtreatment must be fast to avoid structural damage and functional impairment, and the role ofMRI is particularly important for this purpose. Radiologists, in order to have a correct diagnostic approach, have to know the patho-anatomical basis of radiological findings and the main systems of classification and scoring of musculoskeletal lesions.

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