Ankylosing spondylitis can cause disability of the foot. Ankylosing spondylitiis is primarily a disorder with an inflammatory arthritis of the spine, but that inflammatory arthritis can affect any joint. This arthritis is simlar to rheumatoid arthritis, but usually not as severe in the peripheral joints. Heel pain and an inflammation of the midfoot joints are reasonably common. That pain can cause a reasonable amount of disability. The pain in the foot is often hard to treat due to the systemic nature of the condition.
Also, as ankylosing spondylitis affects the spine, especially the lower back resulting in quite a bit of stiffness in the back, it can be hard to reach the feet. This then poses problems about foot self care and this can also result in further disability that may need regular care from a podiatrist.