Which finding on an X-ray is associated with ankylosing spondylitis?

Ankylosing spondylitis is a form of inflammatory arthritis that primarily affects the spine and the sacroiliac joints, leading to pain and stiffness. One of the hallmark radiographic findings associated with advanced ankylosing spondylitis is the presence of a "bamboo spine." This term describes the appearance of the vertebrae as they fuse together, resulting in a rigid, straightened spine that resembles bamboo. The fusion occurs due to the formation of syndesmophytes (bony growths) that bridge adjacent vertebrae, leading to loss of the normal curvature of the spine.

In contrast, the other findings mentioned are not specific to ankylosing spondylitis:

• Joint effusion typically indicates inflammation or injury to a joint but is not characteristic of this condition.

• A salt-and-pepper skull is associated with hyperparathyroidism and certain other conditions affecting bone metabolism, not ankylosing spondylitis.

• Osteoporosis may be a concern related to chronic inflammatory diseases and may occur in various conditions, but it does not specifically indicate ankylosing spondylitis.

Thus, the identification of a "bamboo spine" on X-ray is a defining characteristic that suggests the presence of ank