Radiological study of sacro-iliac joints in ankylosing spondylitis with reference to the evolution of the disease.

Krebs (1931) stated that, in ankylosing spondylitis, sacro-iliac changes appeared early in radiographs and were almost constant. Since that time the attention of all those interested in the clinical aspects and pathogenesis of the disease has been focused on these radiological changes. Scott (1936) laid great stress on the value of radiological changes in early diagnosis of the disease, and launched the idea that sacro-iliac arthritis was possibly the initial focus from which the spinal symptoms developed; being a radiologist, he believed that these radiological changes would not be apparent clinically. Forestier, Jacqueline, and Rotes-Querol (1951) described as symptomatic of sacro-iliac involvement a dull pain referred to the buttocks and the posterior aspect of the thighs. These pains were explained by the exhaustive researches of Lewis (1942) and Kellgren (1955). Forestier (1939) and Forestier and Metzger (1939) have described three stages in the evolution of these radiological changes in the course of the disease,