There is one test witch is not mention in that article witch could confirm or exclude sacroileitis, it’s called Menell catch: patient lie prone and you with one hand put sacrum fixed on bed and with other get the patient bent knee(90 degree) and lift leg of the bed. If the Menell is positive, patient feels pain in Wikipedia reference-linksacroiliac joint. It is the earliest sign of ancylosing spondylitis.