In patients with lower backpain with a pseudoradicular character and pressure pain of the sacroiliac joint might benefit from injections of a local anesthetic in the joint. Furthermore, addition of corticosteroids to the local anesthetic may improve pain relief. Since the literature does not provide consensus regarding the choice of injected anesthetics for this particular pain complaint, we designed a randomized doubleblind placebo-controlled study in which we compare several treatment modalities. With this study we aim to contribute to an improved diagnosis and treatment of sacroiliac complaints. This researchproject will be further elaborated by a retrospective analysis of patient data and anatomic and histologic analysis of the innervation of the sacroiliac joint. This research is embedded in the research institute EMGO.