DKK1 and ankylosis: The role of DKK-1 in the fusion of sacroiliac joints was revealed in human TNF transgenic mice [17]; DKK-1 blockade inhibited bone erosion of the sacroiliac joints and enhanced sacroiliac ankylosis, which strongly supports the potential role of Wnt signaling in the fusion of sacroiliac joints, the hallmark of SpA.