Undifferentiated spondyloarthropathies are a group of diseases that have the clinical, laboratory, and even radiological features of spondyloarthropathies, but do not meet any of the diagnostic criteria for spondyloarthropathies that have been clearly classified to date. uSpA is only a nomenclature, it is neither a disease nor a syndrome in the classification of diseases, it contains several layers of meaning: (i) it may be an early stage of some spondyloarthropathy, which, if left untreated and allowed to progress naturally, can later evolve into any of the typical types of spondyloarthropathies; (ii) it is also possible that some cases may later not develop into typical patients, but become spondyloarthropathies of “abortive” or “tonoplastic” type; (iii) or belong to some overlapping syndrome that cannot be differentiated into some definite spondyloarthropathy; (iv) or some spondyloarthropathy of unknown etiology, which is not yet known but can be clearly classified in the future. uSpA has common manifestations: attachment point inflammation, sacroiliac arthritis, and carriage of the HLA-B27 gene. The most characteristic manifestation of uSpA is arthritis of the attachment points, where the main site of inflammation is the tendon attached to the bone. Lower back pain is the earliest symptom of uSpA, which can radiate to the hip area and thighs and worsen with bed rest and inactivity. uSpA can have various extra-articular manifestations associated with other spondyloarthropathies, such as fever, mouth ulcers, conjunctivitis, iritis, glans ulcers, urethritis, etc. The treatment of uSpA is aimed at reducing pain, relieving symptoms and preventing disability, and its treatment is mostly referred to the treatment of spondyloarthropathies such as ankylosing spondylitis and reactive arthritis.