As you know, ankylosing spondylitis is a systemic immune disease that affects multiple systems and organs and can cause severe disability, for which there is no cure. Once the disease has developed, even with systemic medication, in most cases the disease will progress unnoticed. The disease affects the trunk and can result in spinal ankylosis. Affecting large joints can cause severe functional disability of the lower extremities. Since the disease mostly occurs in young men, one patient can cause a huge financial and emotional burden to a family. In the past two years, we have treated four patients with severe ankylosis of the spine and large joints of the extremities, especially non-functional bony ankylosis of the hip joints bilaterally. My colleague described these patients graphically: they can only do two positions 24 hours a day, either standing or lying down, and they cannot even do their own personal hygiene, which is very painful. There are two types of joint ankylosis: fibrous ankylosis and bony ankylosis. The former means that the joint space can be seen on the X-ray, which means that there is still cartilage in the joint, and the joint has a certain degree of mobility. The latter means that the joint space is lost on the X-ray, and is replaced by bone trabeculae across the joint space. This means that the articular cartilage has been replaced by bone tissue and the joints are fused together, and there is no longer any joint mobility. The progression from fibrous ankylosis to bony ankylosis requires a process. During this process, joint mobility is gradually lost. The same pathological changes in the spine manifest as spinal ankylosis, hence the name ankylosing spondylitis. Treatment of ankylosing spondylitis is still dominated by internal medicine in the early and middle stages. Patients see their doctors mostly for rheumatism, miscellaneous diseases, traditional Chinese medicine, etc. Due to the inconsistent understanding of the pathophysiology and anatomical features of the disease, many patients do not know that surgery can solve some problems, and even in the case of complete bony ankylosis of the joint, still refuse surgery, which is not scientific. Some patients and families, and even some doctors, have the idea that it is not too late to operate if you can avoid surgery. In fact, this understanding is wrong. 1, the loss of joint mobility is not only the loss of articular cartilage, but also the contracture and loss of elasticity of muscle, tendon, ligament, neurovascular tissues, especially in the case of non-functional ankylosis, the soft tissue balance around the joint is severely damaged; 2, in the case of bony ankylosis, even if the joint is operated by international medical masters, the restoration of joint mobility is very difficult. Even if the surgery is performed by international medical masters, it is still very difficult to restore the mobility of the joint, and the limitation of joint mobility will definitely affect the clinical results. In the four severe patients mentioned above, the knee joint had a range of motion of only 50-90 degrees due to the restricted position. The only way to achieve greater intraoperative joint mobility is to perform extensive soft tissue release surgery, which undoubtedly increases the risk and complication rate, and has a negative impact on postoperative joint stability. What can be done? There are several points for patients to learn from: First, while adhering to medical treatment, as long as the blood sedimentation is not too fast, patients should be encouraged to do more joint activities to avoid rapid joint straightening. Two, you can insist on joint massage to help maintain mobility. Third, regular films to understand the loss of articular cartilage. Once the joint space is severely narrowed and the first signs of bony ankylosis appear, you should actively undergo artificial hip replacement surgery, so that you can obtain better joint flexibility and maximize the recovery of joint function after surgery.