What kind of clinical presentation should be suspected for ankylosing spondylitis? Ankylosing spondylitis was previously thought to be more prevalent in men, but recent studies suggest a 2:1 to 3:1 male to female ratio, but women have a slow onset, atypical symptoms, and milder disease. (1) Intermittent pain and/or stiffness in the low back or sacroiliac region, with stiffness evident in the morning; as the disease progresses, it is often accompanied by increased pain at night and difficulty turning over, which interferes with sleep and later develops into a persistent condition. (2) Asymmetric large arthritis or monoarthritis of the lower extremities. The knee, ankle and shoulder joints are the common sites of onset. (3) Several pieces of end-arthritis are common, such as plantar fasciitis and Achilles tendonitis, which manifest as heel pain or tingling on the bottom of the foot. (4) Pain in the buttocks or hip joints. (5) Uveitis and conjunctivitis of the eye. (6) Positive pressure pain in the sacroiliac joint and paravertebral muscles, and limitation of motion in all directions of the spine. (7) Reduction in the extent of thoracic expansion and posterior cervical protrusion. What are the joint manifestations of ankylosing spondylitis? The joints involved in ankylosing spondylitis include the medial joints (sacroiliac and spinal joints) and peripheral joints. (1) Sacroiliac joints: intermittent or persistent lumbosacral or hip pain and stiffness, with a modified version with increased pain at night and difficulty turning over, affecting sleep. Stiffness is obvious in the morning and can be relieved after activity, and physical examination can reveal significant pressure pain in the sacroiliac joints bilaterally. (2) Spine: involving the spine, including the lumbar, thoracic and cervical spine, patients often complain of pain in the low back and restricted movement of the lumbar region, physical examination can be found in all directions of the lumbar region with varying degrees of restriction of movement; positive pressure pain in the lumbar spinous process, paravertebral muscle spasm, pressure pain is obvious, late muscle atrophy, complete ankylosis of the spine, stiffness like an arch, which brings great difficulties to the patient’s life and work. (3) Peripheral joints: 30-40% of spondylitis has peripheral joint involvement as the first symptom, and is more common in women and adolescents. The knee, hip, ankle and shoulder joints are mostly involved, while the small joints of the elbow, hand and foot are occasionally involved, asymmetrically, and single joints or large joints of the lower limbs are mostly involved. Hip involvement is characterized by localized pain, restricted movement, flexion spasm, and can develop joint ankylosis, which is the main cause of disability in this disease.