What is ankylosing spondylitis? Ankylosing spondylitis is a chronic disease whose cause is not well understood and whose main lesion is the spine. The lesion mainly involves the sacroiliac joints, causing spinal ankylosis and fibrosis, resulting in bending, limited walking activities, and various degrees of damage to the eyes, lungs, cardiovascular, kidneys and other organs. Ankylosing spondylitis is more prevalent in young men, with the peak age of onset being around 20 years old. It is also an autoimmune disease because it has varying degrees of ligament, muscle, and bone lesions, as well as autoimmune dysfunction. What bones and joints can be damaged by ankylosing spondylitis? (1) Spine: The sacroiliac joint is a micromobile joint and is the most commonly affected joint in ankylosing spondylitis. (2) Extremity joints: Large joints include the shoulder, elbow, wrist, hip, knee, and ankle; small joints usually refer to the joints of the hands and feet. (3) Structures of movable joints: ligaments, joint capsule, muscles and tendons around joints, articular cartilage, joint cavity, synovial membrane, synovial fluid, etc. Normal synovial fluid has the function of nourishing and lubricating joint cartilage. When inflammation or injury occurs in the joints, fluid accumulates in the joint cavity, which swells and affects the function of the joints. What conditions are present to diagnose ankylosing spondylitis? (1) low back pain and morning stiffness lasting at least 3 months, relieved by exercise and not improved by rest; (2) limited movement in 3 directions of lumbar flexion, back extension and lateral bending; (3) thoracic circumference measured at the level of the 4th rib space, with a difference in exhalation and inspiration mobility of less than 2.5 cm; (4) specific radiological (e.g., x-ray) changes in the sacroiliac joint. What is the difference between HLA-B27 antigen-positive and negative ankylosing spondylitis? The rate of HLA-B27 antigen positivity in patients with ankylosing spondylitis is as high as 90-96%, with less than 10% of patients being HLA-B27 antigen negative. Although HLA-B27-negative and HLA-B27-positive ankylosing spondylitis share common clinical features, there are many differences: HLA-B27 antigen-negative patients are more common in women; age of onset is relatively later than in positive patients; systemic symptoms and peripheral joint changes are less common clinically; acute iritis is less common than in HLA-B27-positive patients; family aggregation is less common than in HLA-B27 There is less family aggregation than in HLA-B27-positive patients, and the involvement of the mid-axis joints is also mild: there are fewer severe changes in the hip joint and changes in blood sedimentation and C-reactive protein due to the disease itself than in HLA-B27-positive ankylosing spondylitis. In conclusion, most HLA-B27-negative patients have a milder disease and better prognosis than HLA-B27-positive patients. Can I get an artificial joint replacement for hip stiffness in ankylosing spondylitis? Artificial joint replacement can be performed, but the functional recovery time after surgery is long and must be adapted to the functional requirements of the joint through prolonged muscle function exercises.