Britannica Sources used in this answer

How does ankylosing spondylitis affect the spine and sacroiliac joints?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Ankylosing spondylitis is a chronic inflammatory condition that primarily targets the sacroiliac joints and the vertebral column.1

The disease typically follows a progressive pattern:

  • Initial Onset: Arthritis first manifests in the sacroiliac joints, which connect the base of the spine to the pelvis.1
  • Progression: Inflammation gradually spreads upward through the spinal column.1
  • Structural Changes: Extensive inflammation leads to the fusion (ankylosis) and deformity of the spine. This process often results in a characteristic "bamboo spine" appearance on radiographs, which signifies the loss of spinal mobility and the development of a rigid, deformed structure.12

Common symptoms associated with this spinal involvement include chronic lower back pain, which often improves with physical activity, and a general limitation in range of motion.12