Reiter's syndrome is a type of arthritis that forms as a reaction to an infection in the body. It involves three conditions: inflammation in and around a joint (arthritis), in the urinary tract (urethritis) and in the lining of the eye (conjunctivitis).

Reiter's syndrome can develop after a person has a gastrointestinal infection or a sexually transmitted disease. However, most people do not develop Reiter's syndrome after having either of these common infections. The reasons that some people develop Reiter's syndrome and others do not are not fully understood.

Two to four weeks after the initial infection, a person with Reiter's syndrome may experience joint pain, commonly in the knees, ankles, feet or lower back. Conjunctivitis makes the eyes red and inflamed. Inflammation in the urinary system causes frequent urges to urinate or a burning sensation during urination. These symptoms may occur together or separately.

There are no specific tests to diagnose Reiter's syndrome. A medical history and description of symptoms can help a physician rule out other conditions and point to Reiter's syndrome.

The infectious symptoms can be treated with antibiotics. The pain and inflammation in the joints may be treated with drugs such as anti-inflammatories. For most patients, treatment resolves symptoms of Reiter's syndrome within several months.