To date, there is no uniform definition of undifferentiated arthritis in the medical community, and the causative factors are not fully understood. It is generally accepted that undifferentiated arthritis can be diagnosed if the symptoms of arthritis in the joints of the extremities do not meet other known diagnostic criteria for arthritis and if the early manifestations of certain connective tissue diseases are excluded. Most patients first present with stiffness and pain in the small joints of the upper extremities, such as the wrist and metacarpophalangeal joints, and then progress to the other joints of the extremities. The course of the disease varies from a few weeks to several years, and some patients may progress to osteoarthritis, systemic lupus erythematosus, and spondylitis in the later stages of the disease, while some patients may have natural remission or no significant changes.