Diagnosis

During the physical exam, your doctor is likely to check your joints for signs and symptoms of inflammation, such as swelling, warmth and tenderness, and test range of motion in your spine and affected joints. Your doctor might also check your eyes for inflammation and your skin for rashes.

Blood tests

Your doctor might recommend that a sample of your blood be tested for:

• Evidence of past or current infection
• Signs of inflammation
• Antibodies associated with other types of arthritis
• A genetic marker linked to reactive arthritis

Joint fluid tests

Your doctor might use a needle to withdraw a sample of fluid from within an affected joint. This fluid will be tested for:

• White blood cell count. An increased number of white blood cells might indicate inflammation or an infection.
• Infections. Bacteria in your joint fluid might indicate septic arthritis, which can result in severe joint damage.
• Crystals. Uric acid crystals in your joint fluid might indicate gout. This very painful type of arthritis often affects the big toe.

Imaging tests

X-rays of your low back, pelvis and joints can indicate whether you have any of the characteristic signs of reactive arthritis. X-rays can also rule out other types of arthritis.