Reactive arthritis 4.4/5 (5)

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Reactive arthritis
Joint inflammation in the left knee. Reactive arthritis attacks one knee most commonly, especially among young men. Wikimedia CC BY-SA 3.0,

Reactive arthritis ICD-10 M02.9


Reactive arthritis is arthritis (arthritis) that occurs after an infection, but without bacteria, viruses or other microbes found in the affected joints. The disease belongs to the group of spondyloarthropathies. Reactive arthritis should not be confused with Septic arthritis where an infection, most often bacteria, is detected in the joints. Reactive arthritis is most often triggered by urinary tract infections, including chlamydia (most often sexually transmitted), and intestinal infections. Symptoms of arthritis, urethritis (urethritis) and eye inflammation (conjunctivitis) was formerly called Reiter's syndrome. Reactive arthritis usually resolves within a few months.

Disease Cause

Infections can cause an over-reaction from immune system so joints, skin, eyes and other organs are mistakenly attacked. People with the hereditary the tissue type HLA-B27 and young men are most vulnerable. Often, the triggering infection is over when the rheumatic symptoms begin (exception is chlamydia infection). The most current triggering bacteria are:


Reactive arthritis typically occurs 1-4 weeks after an infection. Adolescents and adolescents (16-40 years) are most often attacked. Rare among children and the elderly. Men are more commonly attacked than women.

The occurrence (prevalence) worldwide is estimated at 1/1000, but geographical variations exist and the condition is relatively common in Scandinavia (Hayes KM, 2019). Reactive arthritis has been found to account for 18,1% of early arthritis (arthritis with less than 4 months) (Nordli ES, 2017). 


Symptoms of reactive arthritis vary from case to case, making diagnosis difficult in clinical practice (Penis M, 2019). Most typical is stiffness, joint pain and severe arthritis (arthritis), swollen fingers, inflamed tendon attachments and stiffness in the pelvis and lower back (Schmitt SK, 2017). Pelvic, hip or back pain may be due to Iliosacral joints (sakroiliitt) and the back (spondylitis) can be attacked. Inflammatory back pain (gradual onset before 45 years of age, morning stiffness> 45 min, better of physical activity) is then typical. Some people experience persistent discomfort and inflammation in the urethra, some have rashes in the form of nodular rash / erythema nodosum and / or red, unpleasant, inflamed eyes. Most people with reactive arthritis feel generally unwell and some have a fever.


Medical history includes typical symptoms, especially new-onset arthritis and previous signs of urinary tract or gastrointestinal infection in young men.

At clinical examination assess whether there is swelling and heat over affected joints and reduced movement as symptoms arthritis (arthritis). Knees og ankles most often attacked. Other joints, also in the arms and hands are attacked in approx. 50%. If tendons and tendon attachments (enthesitis) is attacked, one can find swelling and increased heat over among other things Achilles Ener. Some fingers or toes may swell to their full length (dactylitis, «Sausage finger»). Eye Inflammation in the form of conjunctivitis, episcleritis, keratitis or uveitis occur.

Blood tests most often shows signs of rheumatic inflammation but elevated CRP and blood drop (SR). HLA B27 is not always tested routinely, but is a predisposing factor (detected in 70-80%, against 8-10% in the southern Norwegian population and approx. 15% in northern Norway).

Urin test. If chlamydia infection is suspected, a urine sample is examined for PCR (morning urine, midstream) in men. Women take a brush sample from the vagina, possibly from the cervix during a gynecological examination (reference: The pages of the National Institute of Public Health).

Joint fluid on swollen joints is on examination thin-liquid and cloudy (yellow-white) without bacteria or uric acid crystals.

Imaging with ultrasound examination confirms signs of arthritis or tendonitis. MRI examination can confirm inflammation and is particularly relevant if reactive arthritis in the pelvis / back with iliosacral joints is suspected.

ECG may be relevant for signs of arrhythmias.


The diagnosis is made on the basis of (reference: Schmitt SK, 2017):

  • Medical history (previous signs of infection (1-4 weeks in advance) with subsequent symptoms from joints, tendon attachments, skin, eyes), especially among young men.
  • Examination (typically arthritis, inflammation of tendon attachments (enthesitis), skin and / or eyes, high CRP and HLA-B27 in blood, imaging).
  • Suspicion of chlamydia infection is tested with a urine sample.

Similar diseases, Differential diagnoses


Most people are referred to a rheumatologist.

  • Joint puncture, tapping of synovial fluid and insertion of Conductor Span or other cortisone in affected joints (reference: Schmitt SK, 2017).
  • Chlamydia infection is treated with antibiotics. In previous gastrointestinal infection, it has generally not been shown that antibiotics have an effect on the intestine or affect the course of arthritis (reference: Barber CE, 2013).
  • Symptoms are reduced with pracetamol, Ibux, naproxen, diclofenac and the like (NSAIDs) painkillers drugs
  • Prednisone tablets with a starting dose of 15-20 mg daily can be used for a few days if joint puncture or painkillers do not have sufficient effect. Dose tapering and ending after a few weeks.
  • Immunosuppressive drugs (DMARDs and biologics) are not usually required, but are used for unusually long-term and debilitating illness. Sulfasalazine (Salazopyrin EN) or methotrexate is then most commonly used. The treatment goal is to prevent erosive disease with permanent joint damage.
  • Eye symptoms treated by an ophthalmologist.


The course varies from person to person. The disease usually returns within 3-5 months, but more chronic courses occur in 10-30% (reference: Carter JD, 2006). In a Norwegian study, after one year, 40% with chlamydia-caused arthritis and 20% with gastrointestinal disease still had some arthritis. After two years, however, 100% of the chlamydia-induced and 95% enteritis-induced had become symptom-free (reference: Glenås A, 1994). Special attention should be paid to chronic arthritis lasting more than six months Ankylosing spondylitis / ankylosing spondylitis or Inflammatory bowel disease as differential diagnoses. 

Guidelines / Recommendations


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