[Roentgen picture of the course of purulent sacroiliitis].

Four patients with extensive iliitis, observed over a period of two to four years, are described. In all patients this disease was unilateral, and more commonly on the right, beginning in the lower half of the joint. Corresponding to the slow development of disease, there were changes in the radiological appearances; these were indefinite in the first two to four weeks. This was followed by an ill-defined appearance, irregularity and widening of the joint space. Healing was characterised by gradual ankylosis and marked sclerosis of both sides of the joint.