Reactive arthritis

Reactive arthritis is inflammation in the joints that an infection somewhere else has set off, most often in the bowel or in the urinary and genital tract. Roused by that infection, the immune system attacks the joints, the tendons and sometimes the eyes, though the joints themselves carry no infection.

Common culprits include bowel infections such as salmonella or campylobacter, and infections caught through sex, chlamydia in particular.

Younger adults are affected most, and after a urinary infection it is commoner in men. People who carry the HLA-B27 gene are more prone to it, and the gene links it with axial spondyloarthritis, psoriatic arthritis and their relatives.

It usually follows an infection by some weeks. Signs to look for:

• Painful, swollen joints, often the knees, the ankles or other large joints of the legs
• A whole finger or toe that swells, or pain where a tendon fixes to the bone
• At times, inflamed eyes or symptoms when passing urine
• An infection of the bowel or urinary tract in the weeks beforehand

Its pattern, the infection that came before it, the examination and tests for inflammation together point to the diagnosis, and the same tests exclude gout and other kinds of arthritis. Being sure of it helps to steer the treatment and gives you a clearer idea of how things are likely to go.

Ultrasound can help to bring inflamed joints and tendons to light. Point-of-care ultrasound is part of the consultation with Dr Borukhson, so the scan can often happen on the day. The ultrasound clinic page walks through what happens during the scan.

Until it settles of its own accord, treatment calms the inflamed joints and relieves the symptoms. Anti-inflammatory tablets (NSAIDs) are often the main tool, and an ultrasound-guided injection may help a single joint that is troublesome.

For the smaller group whose symptoms carry on, come back or settle in for the long term, longer-term treatment is added to get the inflammation under control. If the arthritis goes on, or affects several joints, a standard disease-modifying anti-rheumatic drug (DMARD) such as sulfasalazine or methotrexate is used, with blood tests to keep it safe. If it is still active in spite of them, biologic medicines that block the immune signals behind the inflammation, the anti-TNF treatments for instance, can work well; screening comes first, since these medicines, like the DMARDs, can lower the body's ability to fight infection. Because in many people the arthritis clears up in time, the plan you agree is reviewed as you go, and treatment can be cut back once it settles.

While the inflammation calms down, gentle movement does far more good than lying still. Moving the affected joints as far as is comfortable, with simple exercises through their range, keeps them supple and eases stiffness, and a physiotherapist can show you how.

Pace what you do: rest a joint while it is hot and flared, then build back up step by step. A cold pack in a cloth soothes a swollen knee or ankle for some.

If an infection set it off, finishing any treatment you were prescribed helps, and when an infection caught through sex was the cause, a partner can be tested and treated at a sexual health service, which makes another episode less likely.

Keep your follow-up appointments even when you feel better, since the symptoms now and then come back or linger, and they are easier to handle when they are reviewed early.

The lists below hold the signs that cannot wait, the ones that go beyond the aching, swollen knees, ankles and feet that reactive arthritis brings; the paragraph after them says where to take the rest.

Treat any of these as a 999 or A&E emergency: call 999 and do not drive yourself to A&E.

• Severe illness with suspected sepsis: a high fever with shaking, confusion, rapid breathing, or feeling dramatically worse over hours
• With a fever or feeling unwell, a rash that does not fade when you press it, a stiff neck with eyes that cannot bear bright light, or skin, lips or tongue turning blue, grey, pale or blotchy, since these can be signs of meningitis or sepsis, as can a very bad headache, confusion or a first seizure with a fever or feeling unwell; on black or brown skin the rash and the change of colour may be easier to see on the palms of the hands or the soles of the feet
• A joint you cannot put weight on or move, or that has moved out of place, or, after a fall or injury, very bad pain or any tingling or numbness
• Numbness or tingling around the back passage, genitals or inner thighs, new difficulty passing urine or controlling your bladder or bowels, a change in feeling during sex, or pain, tingling, weakness or numbness in both legs, since these can mean pressure on the nerves at the base of the spine, which needs emergency treatment
• Chest pain that is crushing, tight or like a pressure, that spreads to an arm, the jaw, the neck, the stomach or the back, that comes with breathlessness, sweating, feeling sick or feeling light-headed, or that came on suddenly and does not go away
• Vomiting blood, or bleeding from the back passage that is heavy or will not stop, most of all with faintness, confusion or pain in the abdomen, or vomit that is black or dark brown, since anti-inflammatory tablets, often the main treatment while reactive arthritis settles, can make the stomach bleed
• Lips, mouth, throat or tongue that suddenly swell, a throat that feels tight, very fast breathing or a struggle to breathe or to swallow, skin, tongue or lips turning blue, grey or pale (on black or brown skin this may be easier to see on the palms of the hands or the soles of the feet), becoming suddenly very confused, drowsy or dizzy, or fainting and not being able to be woken, since this can be a severe allergic reaction, anaphylaxis, which can follow a dose of any medicine
• An eye that suddenly and completely loses its sight

Any of these needs an assessment that is urgent, on the same day, from your GP or NHS 111:

• A joint that is hot and swollen, with a fever or feeling unwell, since an infected joint has to be ruled out at once, at A&E or through NHS 111
• A joint that has become hot and very swollen suddenly, or is worsening quickly, even without a fever, since an infected joint does not always announce itself with one
• Joint pain with a fever, or feeling hot, cold or shivery, or generally unwell, since an infection in or around a joint has to be found the same day
• A fever, or feeling generally unwell, on immunosuppressant, biologic or steroid treatment, since an infection has to be treated early; your rheumatology team, if you have one, can be the first call
• Joint pain that simple painkillers such as paracetamol do not control, since pain of that degree needs a doctor's look that day
• Black or dark red stools, on anti-inflammatory tablets, since a bleed in the stomach or gut has to be found that day
• A new red, painful eye, or sight that has blurred, dimmed or changed, which needs an eye casualty or urgent eye clinic the same day, as does an eye that light hurts, since reactive arthritis can inflame the eye, from a sticky conjunctivitis to inflammation deeper inside it; our uveitis guide covers the deeper kind
• Sore joints with pain when you pass urine, a discharge, or a rash or sores on the genitals, since an infection caught through sex may still be there and needs testing and treating; a sexual health clinic can see you too
• Being near someone with measles, chickenpox or shingles, while you take a medicine that weakens the immune system, since measles and chickenpox can be dangerous when the immune system is weakened, and you can catch chickenpox from someone with shingles if you have never had chickenpox; NHS 111 can tell you what to do that day

If reactive arthritis has not been diagnosed and joints have swollen in a way that is new for you, see a GP within days, since a newly inflamed joint should be referred urgently to find its cause. Once reactive arthritis has been diagnosed, a routine review, which your team or GP can arrange, is the place for joints that stay painful or swollen for weeks, return, spread or will not settle on the agreed plan. Back pain with weakness or numbness in one leg, short of the first list, is for your GP, unless the leg is growing weaker or the foot has begun to drag, which needs the same day, from your GP or NHS 111; a leg that suddenly goes weak or numb, with no back or leg pain to explain it, can be a stroke, a 999 or A&E emergency: call 999 and do not drive yourself to A&E. If you cannot tell how urgent something is, asking is never a mistake.

Even though reactive arthritis often gets better on its own, an assessment is how the diagnosis is made certain, the other causes of a hot, swollen joint are excluded and the symptoms are kept in hand. Joints that become swollen soon after an infection are worth a specialist's look, through your GP or booked directly.

What shows that it is reactive arthritis?

No single test proves it, so the diagnosis is pieced together from the way the joints are affected, a recent infection of the bowel or urinary tract, the examination and blood tests. The tests help as well to rule out gout, a different arthritis or some other reason for a hot, swollen joint. Point-of-care ultrasound is part of the consultation with Dr Borukhson, so the joints and tendons can often be checked for inflammation at the same visit, which helps to make the diagnosis clearer.

Will it go away, and can it be cured?

In many people the inflammation calms down over time and the arthritis settles, and a good number make a full recovery. In a smaller number it carries on, returns or becomes long-standing, and then longer-term treatment can bring it under control. A specialist review helps to judge the likely course for you and keeps the symptoms well managed meanwhile.

Is reactive arthritis dangerous?

It is a nuisance more than a danger for most people, and it tends to improve. An assessment is still worthwhile: other causes of a hot, swollen joint need treatments of their own, and inflammation that lingers is easier to manage when it is tackled early. An eye that suddenly and completely loses its sight is a 999 or A&E emergency; red or painful eyes, or any other change in your sight, need an eye casualty or urgent eye clinic the same day, and a joint that has suddenly become very painful, hot and swollen should be seen that day, through A&E or NHS 111 when a fever or feeling unwell comes with it, and otherwise through your GP or NHS 111, as our septic arthritis guide explains.

Will I need an operation?

Surgery is not usually part of it. The aim is to quieten the inflammation and relieve the symptoms, often with anti-inflammatory tablets (NSAIDs); if one joint is especially stubborn, an ultrasound-guided injection may help. Should the symptoms persist, or affect several joints, a medicine that calms the immune response can be added; the plan is yours to agree and is revisited as things change.