Medial spondyloarthropathies are a group of diseases including ankylosing spondylitis, psoriatic arthritis, and enteropathic arthritis, etc. They are prevalent in men, young and middle-aged, and are easily misdiagnosed and missed clinically. Many patients are not diagnosed until the middle and late stages of the disease, which delays the time of treatment. The main clinical manifestation of this disease is inflammatory low back pain, which is characterized by chronic back pain for more than 3 months and at least 4 of the following 5 items are satisfied as inflammatory low back pain ① age <40 years ② insidious onset ③ improvement after activity ④ no improvement after rest ⑤ nocturnal pain (improvement when waking up). If you have inflammatory low back pain, you need to promptly exclude axial spondylolisthesis. The current classification criteria for medial spondyloarthropathy (SPA) proposed by the International Task Force for the Assessment of Ankylosing Spondylitis (ASAS) in 2009 (for patients with low back pain for ≥3 months and age of onset <45 years) are applied: imaging showing sacroiliac arthritis * plus ≥1 SPA features # or HLA-B27 positive plus ≥2 other SPA features # SPA features * imaging showing sacroiliac arthritis l Inflammatory low back pain l Arthritis l Adnexitis (heel) l Uveitis l Finger or toe inflammation l Psoriasis l Crohn's disease colitis l Good NSAID therapy l Family history of SPA l HLA-B27 l Elevated CRP l MRI showing active (acute) inflammation highly suggestive of SPA-related sacroiliac arthritis l Definite radiographic sacroiliac arthritis according to the revised New York criteria