In young people, spondylitis usually starts in a leg joint such as the ankle or knee, or where the leg meets the pelvis in the hip. It may take months or sometimes years for other areas to be affected, like the spine.
In each person the disease can behave somewhat differently. Sometimes the first symptom of spondylitis is pain and tenderness due to inflammation in the ligaments and tendons where they attach to the bone, which is called enthesitis. In this case the pain is not in the joint but instead occurs near or around the joint. In young people enthesitis is most common under the heel on the bottom of the foot, behind the heel (Achilles tendon), under the toes where they attach to the foot, or around the kneecap. About 20% young people with spondylitis develop inflammation in the eye called uveitis (or acute anterior uveitis) or iritis. When this occurs it usually causes pain, redness, and sensitivity to light, and it can occur in one or both eyes at the same time.
Sometimes people develop other symptoms as well. These include fever, psoriasis (a chronic skin rash), other rashes, colitis or Crohn's disease (inflammation of the intestines).
Young people with spondylitis sometimes have symptoms that are episodic and unpredictable, seeming to come and go without an obvious cause over a long period of time. This cycle of disease flare up followed by remission may be repeated many times.
It is important to note that the disease progression and the severity of symptoms vary in each person. Some teens may experience a mild, short-term disease, whereas others might experience more severe symptoms.