Sacroiliac arthritis is not spondylitis, but sacroiliac arthritis is a clinical manifestation of spondylitis. Sacroiliac arthritis is divided into primary sacroiliac arthritis and secondary sacroiliac arthritis. Primary sacroiliac arthritis is often aseptic inflammation of the sacroiliac joints, often with significant pain at night or in the morning, relieved by activity, and rarely with manifestations outside the sacroiliac joints. Secondary sacroiliac arthritis is often secondary to ankylosing spondylitis, endocrine disorders, trauma, etc. Spondylitis, also known as spondyloarthropathies, is a group of diseases linked in clinical manifestations and genetic susceptibility, including ankylosing spondylitis, undifferentiated spondyloarthritis, inflammatory bowel disease arthritis, and reactive arthritis. Its main manifestation is asymmetric inflammation of the mid-axis joints, including sacroiliac arthritis and spondylolisthesis. If sacroiliac arthritis or spondylolisthesis is diagnosed, early and standardized treatment is recommended to reduce the adverse effects of the disease.