Computer tomography, like conventional radiography, can demonstrate inflammatory, degenerative or reparative, traumatic and neoplastic lesions of the sacroiliac joints. In some cases computer tomography adds important information, for instance as regards soft tissue changes near the S.I. joints in the presence of neoplastic or posttraumatic lesions (tumour extension, hematoma). Computer tomography is also able to demonstrate minor disalignment of the sacro-iliac joints (so-called sacro-listhesis).