The most common early symptoms of AS are frequent pain and stiffness in the lower back and buttocks. At first, discomfort may only be felt on one side or alternate sides.
The pain and stiffness are usually worse in the mornings and at night. Also, in the early stages of AS, there may be a mild fever, loss of appetite, and general discomfort. It is important to note that back pain from AS is inflammatory and not mechanical.
This pain may become persistent and is felt on both sides, usually lasting at least three months. Over months or years, the stiffness and pain can spread up the spine and into the neck. Pain and tenderness spreading to the ribs, shoulder blades, hips, thighs, and heels is also possible.