In the last century, if rheumatoid arthritis was suspected at the time of medical consultation, it was important to see if the rheumatoid factor (RF) was positive and to take X-rays to see if there was joint swelling in the finger joints and wrist joints and worm-like destruction of the joint bones, and to assume that the joint lesions seen in this type of rheumatoid arthritis should be symmetrical. Today, with advances in imaging techniques, the diagnostic aspects of the examination of the disease have been updated. The diagnostic criteria promulgated in 1987 are no longer applicable. In 2010, the American College of Rheumatology and the European League Against Rheumatism officially promulgated new diagnostic criteria for rheumatoid arthritis, which include MRI as an important imaging test for the early diagnosis of rheumatoid arthritis and emphasize that enhanced MRI scans should not be ignored. This enables the detection of the basic, early lesions of rheumatoid arthritis, namely: rheumatoid synovitis, and osteoedema, which represents early or active disease. These lesions are the only ones that can be detected by magnetic resonance. The significance of this is that early detection, diagnosis and timely treatment can effectively reduce the disability rate of the disease. Therefore, it is not enough to take an X-ray of the hand or wrist to check whether there is rheumatoid arthritis in the hospital, because the synovial membrane and other soft tissue lesions in the early stages of the disease cannot be seen in this examination. Bone edema cannot be seen either. CT examinations are somewhat clearer than radiographs in terms of bone structure, but they are not as good as MRI for the soft tissue lesions and bone edema mentioned above, or they cannot be seen. What is the significance of a positive/negative rheumatoid factor (RF) test for rheumatoid arthritis diagnosis? A positive blood test is only a reference and is not an absolute indicator for the diagnosis of rheumatoid arthritis, which means that a positive RF test does not necessarily mean that the disease is present, while a negative RF test does not necessarily mean that the disease is not present. Regarding the symmetry of the affected joints, the new diagnostic criteria are no longer mentioned, which means that the affected joints of rheumatoid arthritis do not necessarily have a “one-to-one symmetry”. The above shows that magnetic resonance imaging (plain plus enhanced) is very important in the diagnosis of rheumatoid arthritis.