Reactive arthritis is joint pain and swelling that starts after an infection elsewhere in your body

Reactive arthritis happens when your immune system overreacts to an infection — usually in your gut, urinary tract, or after a sexually transmitted infection — and causes inflammation in your joints. The infection itself may be mild or already cleared, but your body's response lingers in your knees, ankles, feet, or other joints. It typically appears one to three weeks after the triggering infection and can last weeks or months.

The condition is different from rheumatoid arthritis, where your immune system attacks your joints directly over time. With reactive arthritis, the joint pain is a side effect of fighting off an infection somewhere else. Most people recover fully, though some experience flare-ups or longer-lasting joint problems.

Key Takeaways

  • Reactive arthritis develops after a bacterial infection in your gut, urinary tract, or from a sexually transmitted infection, not from the infection in your joints themselves.
  • Symptoms include joint swelling and pain (especially in knees and ankles), eye redness, and sometimes urinary or digestive symptoms, appearing one to three weeks after the initial infection.
  • A doctor diagnoses reactive arthritis by asking about recent infections and examining your joints; there is no single test that confirms it.
  • Most cases resolve on their own within a few months, though anti-inflammatory medications and rest speed recovery.
  • A small number of people develop longer-lasting joint problems or experience repeated flare-ups, particularly if they carry a genetic marker called HLA-B27.

What infections trigger reactive arthritis

The most common trigger is a bacterial infection in your digestive tract — often from contaminated food or water. Bacteria like Salmonella, Shigella, Yersinia, and Campylobacter can start the chain reaction. You may have had diarrhea or stomach cramps a few weeks before your joints started hurting.

Urinary tract infections and sexually transmitted infections, particularly chlamydia, are also frequent triggers. In some cases, the original infection was so mild you barely noticed it — a brief bout of loose stools or mild urinary symptoms — and then weeks later your knees swell up.

Reactive arthritis is not contagious from person to person. You cannot catch it from someone who has it. However, the underlying infection that triggered it (like food poisoning or chlamydia) can spread, so the original infection itself may need treatment.

Symptoms beyond joint pain

Joint swelling and pain are the main signs, usually in your knees, ankles, heels, or feet, though it can affect other joints too. The pain often feels worse in the morning or after you have been sitting still, and it may improve with movement.

Many people also experience eye redness and irritation (conjunctivitis), sometimes without pain. A smaller number develop urinary symptoms like painful urination or increased urgency, or ongoing digestive symptoms. These extra symptoms, combined with joint pain after a recent infection, help doctors recognize reactive arthritis rather than another type of arthritis.

Fatigue and low-grade fever sometimes accompany the joint symptoms. The overall picture — joint pain plus eye or urinary symptoms after a known infection — is what points toward reactive arthritis.

How doctors recognize reactive arthritis

Your doctor will ask detailed questions about any infections you had in the past month or two, including food poisoning, diarrhea, urinary tract infections, or sexually transmitted infections. They will examine your joints for swelling and ask about pain patterns. They may also ask whether your eyes have been red or irritated.

Blood tests can show signs of inflammation (like elevated inflammatory markers), but they do not directly prove reactive arthritis. X-rays of affected joints may rule out other problems. There is no single test that confirms reactive arthritis — diagnosis rests on the pattern of symptoms and the timing after an infection.

Your doctor may test for the HLA-B27 genetic marker, which some people carry. If you have it, your risk of longer-lasting joint problems is higher, though many people with HLA-B27 never develop reactive arthritis at all.

Treatment and recovery timeline

Most cases of reactive arthritis improve on their own within a few weeks to a few months. Rest, ice, and over-the-counter anti-inflammatory medications like ibuprofen or naproxen reduce swelling and pain while your immune system settles down. Elevating the affected joint and avoiding activities that aggravate it speed recovery.

If the original infection (like chlamydia or food poisoning) is still being treated, completing that treatment is important. Your doctor may prescribe stronger anti-inflammatory medications or, in longer-lasting cases, medications that suppress immune activity.

Physical therapy is sometimes recommended if joint stiffness lingers after the acute pain fades. Most people return to normal activity without lasting damage, though recovery pace varies.

When reactive arthritis becomes long-term

In most cases, reactive arthritis clears completely within three to twelve months. However, some people — particularly those who carry the HLA-B27 genetic marker — experience symptoms that last longer or return in flare-ups over months or years.

A small number develop chronic joint damage or ongoing inflammation that resembles other forms of arthritis. This is less common but more likely if you have HLA-B27 or if the initial infection was severe. Regular follow-up with your doctor helps catch any signs of longer-term problems early.

Even if symptoms persist, they often become milder and more manageable over time. Staying active within the limits of your pain, maintaining a healthy weight, and managing stress all support joint health during recovery.

Frequently Asked Questions

Can reactive arthritis come back after it goes away?

Yes, some people experience flare-ups or recurrence, especially if they carry the HLA-B27 genetic marker or if they have another triggering infection. However, most people who recover from reactive arthritis do not have it happen again. If you develop joint pain after a new infection, tell your doctor about your previous reactive arthritis.

Is reactive arthritis the same as rheumatoid arthritis?

No. Reactive arthritis is triggered by an infection and usually resolves within months. Rheumatoid arthritis is a chronic autoimmune condition where your immune system attacks your joints over years or a lifetime. The causes, treatments, and long-term outlook are very different.

Do I need antibiotics to treat reactive arthritis?

Antibiotics treat the underlying infection that triggered it (like chlamydia or food poisoning), not the joint inflammation itself. If the infection has already cleared, antibiotics will not help the arthritis. Your doctor will decide whether the original infection still needs treatment based on what caused it and how long ago it occurred.

What should I do if my joint pain does not improve after a few weeks?

Contact your doctor. While most reactive arthritis improves within weeks, some cases take longer or require stronger anti-inflammatory treatment. Your doctor can rule out other causes of joint pain and adjust your treatment plan if needed.