Last reviewed 07/2021
Ankylosing spondylitis primarily affects the cartilaginous joints of the spine and the sacro-ilium. Disease of synovial joints resembles rheumatoid arthritis.
There is progressive ankylosis of affected joints. Initially a vascular fibrous tissue bridges the joint space followed by ossification.
In the spine there is progressive replacement of the nucleus pulposus, nucleus fibrosus and the articular surfaces of the vertebral bodies with fibrous tissue. As the fibrous tissue ossifys the characteristic radiographic findings of a bamboo spine become apparent.
The stiff spine becomes osteoporotic and prone to fractures following minor trauma.