There are five grades used to diagnose the severity of sacroiliitis, with grade 0 being perfectly normal (or just no presence of sacroiliitis), grade 1 being early indicators that lead to suspicion or testing, grade 2 which is the presence of small erosions, grade 3 having definitive erosions, and grade 4 involving noticeable immobility or stiffening of the joint. Each grade is indicative of the progression of the inflammation. Early detection is key for effective and easier treatment and to prevent development into later grades. However, diagnosis is not typically able to be considered positive for sacroiliitis until it has progressed to grade 2 or 3 as it can be easily conflated with other causes of lower back pain if there is not visible inflammation being picked up by diagnostic tools.