[Imaging of infectious sacroiliitis]

About 11 cases of various infectious sacroiliitis, the authors discuss the clinical, biological and radiological findings. Acute and subacute infectious sacroiliitis can be associated with another arthritis and are often accompanied by soft tissues lesions. Radiological investigations are very useful for the diagnosis, because of the unspecific clinical and biological findings. Radiography shows advanced osteoarticular remodelling but the subtle lesions are often unapparent. Bone scintigraphy shows a focal hypercaptation but is unspecific. Tomography and CT point out the erosions. With CT, soft tissues lesions are well demonstrated and a diagnostic punction with a fine needle is easily guided. MRI can indicate a bone marrow oedema and her quality for soft tissues lesions is well known; for these reasons, it could become a technic of choice.