Ankylosing spondylitis is a disease with clinically and radiologically very 
variable features. It is the intention to direct the attention from the old by 
orthopedists' influenced association of the stiff back to the polymorphism of 
the disease especially to the early stages which still frequently are recognized 
too late. The paper deals with the nosology, the various states of the clinical 
course with the numerous radiological criteria including therapeutical 
approaches.