Inflammation of the entheses, where joint capsules, ligaments, or tendons attach to bone, is a hallmark of ankylosing spondylitis (AS). This can be felt in multiple areas of the body, where doctor can check for pain and tenderness.
The sites are sometimes referred to as “hot spots.” They can lead to swelling and tenderness along the back, pelvic bones, sacroiliac joints, the chest, and the heel. The heel can be significantly affected, and the pain and tenderness can have a serious impact on a person’s mobility. The two areas of the foot that can be affected are the Achilles tendon, at the back of the heel and the plantar fascia, at the base of the heel.