Ankylosing spondylitis is also a rheumatic disease that is seronegative arthritis. The vast majority of arthritic lesions in ankylosing spondylitis first invade the sacroiliac joints and later progress upward to the cervical spine. In a few patients, the cervical spine or several spinal segments are invaded at the same time, and the surrounding joints may also be invaded. In the early stages of the disease, there is inflammatory pain in the joints, accompanied by muscle spasms around the joints and a feeling of stiffness, which is obvious in the morning; it may also manifest as nighttime pain, which is relieved by activities or painkillers. As the disease progresses, the joint pain decreases, while the movement of each segment of the spine and joints is restricted and deformed. In advanced stages, the entire spine and lower limbs become strongly bowed and flexed forward. Here are the specific symptoms of joint lesions. 1, sacroiliac arthritis: about 90% of AS patients are first manifested as sacroiliac arthritis. Later, it develops upward to the cervical spine and manifests as recurrent lumbar pain, lumbosacral stiffness, intermittent or alternating lumbar pain and hip pain on both sides, which can radiate to the thighs, without positive signs and negative extension and leg lift test. However, direct pressure or extension of the sacroiliac joint can cause pain, so it is not like sciatica. Some patients have no symptoms of sacroiliac arthritis and only abnormal changes are found on X-ray. About 3% of AS cervical spine is involved at the earliest, and later it progresses down to lumbosacral region, and 7% of AS has several spinal segments involved at the same time. 2, lumbar spine lesions: when the lumbar spine is involved, most of them show restricted movement of the lower back and lumbar region. Lumbar forward flexion, lateral bending and rotation can be limited. Physical examination may reveal lumbar spine prominence pressure pain, lumbar paraspinal muscle spasm; later there may be lumbar muscle atrophy. 3, thoracic spine lesions: when the thoracic spine is involved, it is manifested as back pain, anterior and lateral chest pain, and carrying arms like hunchback deformity. If the rib spine joint, sternal stalk joint, sternoclavicular joint and intercostal cartilage joint are involved, there is a bundle-like chest pain, restricted thoracic expansion, and the chest pain is aggravated when inhaling and coughing or sneezing. In severe cases, the thorax remains in the expiratory state, and the expansion of the thorax is reduced by more than 50% compared with normal people, so it can only be assisted by abdominal breathing. Due to the reduction of thoracic and abdominal cavity capacity, it causes cardiopulmonary and digestive dysfunction. 4. Cervical spine lesions: A few patients first show cervical spine inflammation, with pain in the cervical spine first, radiating along the neck to the head, shoulder and arm. The muscles of the neck start to spasm and later atrophy, and the lesion progresses to cervicothoracic posterior convexity deformity. Head movement is significantly limited, often fixed in a forward-flexed position, unable to supinate, lateral bend or rotate. Severe cases can only see a small piece of ground in front of their toes, and cannot raise their heads to look flat. 5. Peripheral arthropathy: About half of the AS patients have transient acute peripheral arthritis, and about 25% have permanent peripheral joint damage. It generally occurs more often in large joints and more in the lower extremities than in the upper extremities. According to some statistics, the rate of peripheral joint involvement is 40% for the hip and shoulder, 15% and 5% for the knee, 10% for the ankle, 5% for the foot and wrist, and very rarely for the hand. The hospital reported 80 cases of AS with hip involvement (100%); limitation of movement (64%), flexion contracture (38%), muscle atrophy (25%), and joint ankylosis (37%) were the main causes of disability in AS patients; 94% of hip symptoms appeared within 5 years of onset, suggesting that if the hip joint is not involved in the first 5 years of AS onset, it is unlikely to be involved later. When the shoulder joint is involved in AS patients, the pain is more pronounced when the joint movement is restricted, and activities such as combing hair and lifting hands are limited. When the knee joint is involved, the joint is compensated for bending, making daily life such as walking and sitting more difficult. It rarely affects the elbow, wrist and foot joints, and is even rarer when it affects some of the joints. Ankylosing spondylitis is very dangerous for patients, and if the disease is not controlled, AS patients will have limited activities and a very low quality of life in the late stages of the disease.