Living With Arthritis
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Reactive arthritis symptoms

Reactive arthritis is joint inflammation triggered by an infection elsewhere in the body — usually a gut or urinary infection. Symptoms typically appear 2–4 weeks after the triggering infection, which may already have settled, so people often do not connect the two.

Common symptoms of reactive arthritis

  • Joint pain and swelling, often in the knees, ankles, or feet
  • Lower back or buttock pain
  • Heel pain (enthesitis)
  • Dactylitis — sausage-like swelling of a toe or finger
  • Eye inflammation (conjunctivitis or uveitis)
  • Burning on passing urine, even after the triggering infection has cleared

When to see your GP

See your GP if you develop joint pain and swelling within a few weeks of a gut or urinary infection. Mention the recent infection — it's an important clue for diagnosis.

The infection-to-joint timeline

A typical UK story is a week of diarrhoea after travel or a takeaway, or a urinary infection, then a quiet fortnight, then a knee or ankle that swells almost overnight. The germ has usually gone; the immune system is still reacting. That is why antibiotics for the joint itself are often not the answer once the original infection has cleared. Write the dates down — rheumatology letters are easier when the timeline is clear.

How this differs from septic arthritis

A single extremely hot joint with fever and inability to move it can be infection inside the joint — a same-day emergency. Reactive arthritis more often involves more than one joint, follows a recent gut or urinary illness, and the person is less systemically toxic. If you are unsure which you have, treat it as urgent. A GP or emergency department can rule out sepsis and crystal arthritis before labelling it reactive.

Eyes, heels and the classic pattern

The old teaching triad — arthritis, urethritis, conjunctivitis — still appears, but many people have only two of the three. Heel pain and a swollen 'sausage' toe are as useful as a red eye. Lower back or buttock pain can look like a slipped disc. If you have recently had chlamydia or a gut infection, say so; sexual-health and stool history changes the blood tests a GP orders.

This is general information, not a substitute for personalised medical advice.

Frequently asked questions

What are the first signs of reactive arthritis?

A knee, ankle or foot that swells one to four weeks after a gut or urinary infection is the typical start. Heel pain, a sausage-like toe, red eyes or burning urine can appear even after the original infection has gone.

How is reactive arthritis diagnosed in the UK?

Diagnosis is clinical: the timeline plus examination. A GP or emergency team must first rule out a septic (infected) joint. Stool, urine or sexual-health tests look for a still-active trigger. There is no single blood test that proves reactive arthritis.

Can reactive arthritis symptoms come and go?

Yes. Swelling can shift between joints. Most people improve over weeks to months. A sore heel or stiff knee can linger after the dramatic swelling has gone. Disease that stays active beyond six months needs a rheumatology review.

When should I see a GP about reactive arthritis?

See a GP if joint swelling appears within weeks of diarrhoea or a urinary infection. Go urgent the same day if one joint is extremely hot, you cannot weight-bear, or you have a high fever — that may be septic arthritis, not reactive disease.

Is reactive arthritis the same as septic arthritis?

No. Septic arthritis is infection inside the joint and is an emergency. Reactive arthritis is an immune reaction after an infection elsewhere. If you cannot tell them apart, treat it as urgent and let a clinician decide.