In the last few years of outpatient work, we have seen many patients who presented with postpartum low back pain, which worsened at night, with a CT diagnosis of dense sacroiliac arthritis. Because the pain appeared in the postpartum period, some were diagnosed as postpartum rheumatism. Again, because of the characteristics of low back pain, some were diagnosed as ankylosing spondylitis and were even recommended for biologic agents. Such patients are specifically warned that they do not need to use biologics, which will not make much sense for such patients and will not have a greater therapeutic effect, in addition to increasing the financial burden and risk. How can this disease be distinguished from ankylosing spondylitis? Is it related to postpartum rheumatism? Is its treatment different from postpartum rheumatism? The stability of the sacroiliac joint in women is affected during childbirth, the surrounding ligaments are relaxed, and the abnormal stresses on the iliac bone itself and the joint locally increase; in addition, the angle of sacral tilt increases, the pelvis tilts forward and down, and the pulling of the ligaments attached to the iliac bone affects the blood flow of the iliac bone, causing dense changes in the bone due to reduced local blood supply. Ankylosing spondylitis has erosive changes on CT, whereas dense sacroiliitis does not have this feature. The main manifestation is pain in the lumbosacral or lower back, with occasional radiating pain toward the buttocks in the lower buttocks and posterior thighs. The patient is full-bodied and has a large lumbosacral angle, and the sacrospinous muscles are mostly in tension, with positive pelvic separation test and “4” test. The patient had a normal hematocrit and no bacterial inflammatory manifestations. Radiology mainly showed increased bone density in the iliac auricle near the sacroiliac joint surface, with a uniform dense white triangular bone dense zone with clear edges, disappearance of bone trabeculae, neat and clear sacroiliac joint gap, and no bone destruction. As for HLA-B27 negative, positive or not, it has no diagnostic significance for this disease. Dense sacroiliac arthritis is mainly treated with non-surgical therapy. For mild symptoms, bed rest is appropriate, and protection with an elastic peri-waist is advisable after getting out of bed; for severe symptoms, pain relievers can be given, although there is no evidence of an inflammatory factor in this disease, so the indications for the application of NSAIDs are not clear. The patient is also protected with a brace, and when the pain subsides, the patient is encouraged to do abdominal exercises and continues to be protected with an elastic lumbar girth. For those with intractable pain, sacroiliac joint fusion surgery can be considered. Are there other ways to treat this dense sacroiliac arthritis? Is there any difference from the treatment of postpartum rheumatism? Chinese medicine is very effective in the treatment of dense sacroiliac arthritis, and many patients can quickly relieve their symptoms and go to work and start normal work and study after receiving evidence-based treatment from Chinese medicine. For postpartum dense sacroiliac arthritis, it is important to consider the characteristics of the patient’s postpartum period. These patients have some common features with other postpartum rheumatism. After consuming qi and hurting blood, they feel the evil of cold and dampness, both the characteristics of qi and blood deficiency and cold and dampness invasion, postpartum rheumatism and postpartum dense sacroiliac arthritis should be properly dispersed cold and dispel dampness on the basis of replenishing qi and nourishing blood, do not use too much medicine to dispel wind and dampness, so as not to further consume qi and hurt qi and blood. However, postpartum dense sacroiliac arthritis is different from postpartum rheumatism in that this disease also has injury and may be mixed with blood stasis. In addition to dispersing cold and dispelling dampness on the basis of benefiting qi and nourishing blood, attention should also be paid to appropriately invigorate blood and dispel stasis. When treating postpartum diseases in TCM, we must pay attention to the characteristics of postpartum qi depletion and blood injury. After correct TCM diagnosis and treatment, postpartum dense sacroiliac arthritis can be well controlled like other postpartum rheumatism.