A person with ankylosing spondylitis commonly will feel pain or stiffness in the lower back, especially in the morning or after periods of inactivity. Usually, back pain begins in the sacroiliac joint and works its way up the lower spine. Eventually, the disorder can affect the entire spine. People can have pain and tenderness in the thighs, hips and other joints of the torso. Knees and ankles can be inflamed as well, although it usually affects no more than three or four joints in the arms and legs.
One feature of ankylosing spondylitis is that stiffness often improves with activity. People who have this disorder may get worse if they do not exercise regularly. (Back pain from many other causes tends to worsen with exercise.) As the spine and its supporting structures stiffen, a person may begin to stoop over. With time, the bones of the spine can fuse or grow together, causing an extremely stiff, rigid backbone called a poker spine. This may make it difficult to take a deep breath because the rigid spine and stiff joints between the ribs and breastbone make it difficult for the chest to expand. In rare cases, inflammation in the lungs causes shortness of breath and inflammation in the eyes may cause reduced vision with red, painful eyes. The pain and rigidity in the lower back can cause problems walking. Almost any movement can become extremely painful.
Other possible symptoms of ankylosing spondylitis include:
Loss of appetite