Which of the following is a classic example of peripheral involvement in Ankylosing Spondylitis?

• A. IBD
• B. Aortitis
• C. Knee bursitis
• D. Uveitis

Answer: (C)

In Ankylosing Spondylitis, inflammation isn’t limited to the spine; peripheral involvement refers to inflammation of joints or periarticular structures outside the axial skeleton. The knee is a common site for this pattern, typically manifesting as inflammation around the joint such as bursitis—the knee’s periarticular bursa becomes inflamed, producing swelling and pain with movement. This represents a peripheral, soft-tissue joint involvement rather than axial spine disease.

Other options illustrate extraspinal organ involvement rather than peripheral joints: uveitis affects the eye, aortitis involves the blood vessel wall, and inflammatory bowel disease affects the gut. So knee bursitis best showcases peripheral joint/soft-tissue involvement in AS.