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# Reactive arthritis

Joint inflammation that starts a few weeks after a gut or genital infection, without germs in the joint. It can also inflame the eyes and urethra.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Joint capsule](https://durgical.com/en/anatomy/articular-capsule-of-knee-joint/)
- [Achilles tendon](https://durgical.com/en/anatomy/calcaneal-tendon/)
- [Urethra (male)](https://durgical.com/en/anatomy/male-urethra/)
- [Plantar fascia](https://durgical.com/en/anatomy/plantar-aponeurosis/)
- [Calcaneus](https://durgical.com/en/anatomy/calcaneus/)
- [Toe joint capsules](https://durgical.com/en/anatomy/capsules-of-metatarsophalangeal-and-interphalangeal-joints-of-foot/)
- [Sacroiliac ligaments](https://durgical.com/en/anatomy/sacroiliac-ligaments/)
- [Cornea](https://durgical.com/en/anatomy/cornea/)
- [Prostate](https://durgical.com/en/anatomy/prostate/)

## Why it happens

- [Innate and adaptive immunity: overview](https://durgical.com/en/physiology/innate-and-adaptive-immunity-overview/)
- [Synovial joints: capsule, synovial membrane and articular cartilage](https://durgical.com/en/histology/synovial-joints-capsule-synovial-membrane-and-articular-cartilage/)

## What it is

A sterile inflammatory arthritis that appears one to four weeks after a gastrointestinal or genitourinary infection. It belongs to the spondyloarthritis family and typically causes asymmetric arthritis of the legs, enthesitis and sometimes eye and urethral inflammation.

## Who gets it

Mostly affects young adults aged 20 to 40. After sexually transmitted chlamydia it is more frequent in men; after enteric infection both sexes are affected equally. In Colombia and Latin America, where acute diarrhoeal disease and sexually transmitted infections remain common, it is a relevant cause of acute arthritis in young people.

## Causes

- Genitourinary infection: Chlamydia trachomatis
- Enteric infection: Salmonella, Shigella, Campylobacter, Yersinia and Clostridioides difficile
- Immune reaction to bacterial antigens that reach the joint; the joint fluid is sterile on culture

## Risk factors

- HLA-B27 (more severe and chronic disease)
- Young adult age
- Unprotected sex and sexually transmitted infections
- Food-borne gastroenteritis
- HIV infection

## Pathophysiology

After a mucosal infection, bacterial antigens and fragments are carried to the synovium and entheses, where they trigger an immune response in genetically predisposed people, especially HLA-B27 carriers. Inflammation targets the joints, tendon insertions, the eye and the mucous membranes, without live bacteria growing in the joint.

## Symptoms and signs

- Asymmetric arthritis of a few large joints of the legs (knees, ankles, feet), 1 to 4 weeks after diarrhoea or urethritis
- Heel pain from enthesitis at the [Achilles tendon](https://durgical.com/en/anatomy/calcaneal-tendon/) or plantar fascia insertion
- Sausage-shaped toes or fingers (dactylitis)
- Low back or buttock pain (sacroiliitis)
- Red eyes (conjunctivitis) or painful red eye with blurred vision (anterior uveitis)
- Burning urination and discharge (urethritis or cervicitis)
- [Skin](https://durgical.com/en/anatomy/skin/) and mucosal lesions: keratoderma blennorrhagicum of soles and palms, circinate balanitis, painless mouth ulcers

## Red flags

- Single hot swollen joint with fever: septic arthritis must be excluded by joint aspiration
- Painful red eye with photophobia or visual loss (anterior uveitis)
- Suspected disseminated gonococcal infection (skin pustules, tenosynovitis)
- Symptoms suggesting HIV infection or other sexually transmitted infections

## Diagnosis

**Clinical**
Clinical diagnosis based on typical arthritis and enthesitis following a recent diarrhoeal or genitourinary infection; the triad of arthritis, conjunctivitis and urethritis is classic but often incomplete.

**Tests**
Raised ESR and CRP; nucleic acid amplification tests for chlamydia and gonorrhoea in urine or swabs; stool culture if diarrhoea persists. Joint aspiration shows inflammatory, culture-negative fluid without crystals. HLA-B27 supports the diagnosis and predicts chronicity; HIV and syphilis testing are offered.

**Imaging**
Radiographs are often normal early; later they may show enthesophytes (heel spurs) and asymmetric sacroiliitis. MRI or ultrasound detect sacroiliitis and enthesitis.

## Differential diagnosis

- Septic arthritis, including gonococcal arthritis
- Gout and pseudogout
- Psoriatic arthritis
- Ankylosing spondylitis
- Enteropathic arthritis (inflammatory bowel disease)
- Post-streptococcal arthritis and rheumatic fever
- Viral arthritis (chikungunya, parvovirus B19)

## Goal of treatment

Treat any persisting infection and its sexual partners, control joint and eye inflammation, and preserve function while the disease usually remits.

## Treatment

**Medical**
Non-steroidal anti-inflammatory drugs are the first-line treatment for arthritis and enthesitis.

**Medical**
Antibiotics treat an active chlamydial infection (and sexual partners); they do not shorten arthritis after enteric infection. Intra-articular glucocorticoids once infection is excluded; topical eye glucocorticoids for uveitis under ophthalmology care.

**Medical**
Disease-modifying drugs (sulfasalazine, methotrexate) and, for refractory cases, TNF inhibitors in chronic disease.

**Rehabilitation**
Rest of acutely inflamed joints, then physiotherapy and stretching of the Achilles and [plantar fascia](https://durgical.com/en/anatomy/plantar-aponeurosis/) to maintain movement.

## Complications

- Chronic or recurrent arthritis (more likely with HLA-B27)
- Progression to chronic spondyloarthritis with sacroiliitis
- Recurrent anterior uveitis and vision loss if untreated
- Aortic regurgitation and conduction defects (rare)
- Joint damage and disability

## Prognosis

Most attacks settle within 3 to 12 months. A minority, more often HLA-B27 carriers, develop recurrent or chronic arthritis or a persistent spondyloarthritis.

## Prevention

- Safe food and water handling to prevent enteric infections
- Condom use and screening of sexually transmitted infections
- Prompt treatment of chlamydial infection in patients and partners

## Test yourself

Think of the answer, then tap the question to see it.

## Which infections typically trigger reactive arthritis?

Chlamydia trachomatis urethritis and enteric infections with Salmonella, Shigella, Campylobacter or Yersinia.

## What is the classic triad of reactive arthritis?

Arthritis, conjunctivitis and urethritis, often incomplete.

## Which HLA allele is associated with reactive arthritis?

HLA-B27, which predicts more severe and chronic disease.

## What must be excluded in a single hot, swollen joint before diagnosing reactive arthritis?

Septic arthritis, including gonococcal arthritis, by joint aspiration with Gram stain and culture.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/conditions/reactive-arthritis/)

## Related conditions

- [Chlamydia infection](https://durgical.com/en/conditions/chlamydia-infection/)
- [Gonorrhoea](https://durgical.com/en/conditions/gonorrhoea/)
- [Conjunctivitis](https://durgical.com/en/conditions/conjunctivitis/)
- [Uveitis](https://durgical.com/en/conditions/uveitis/)
- [Ankylosing spondylitis](https://durgical.com/en/conditions/ankylosing-spondylitis/)
- [Psoriatic arthritis](https://durgical.com/en/conditions/psoriatic-arthritis/)
- [Septic Arthritis of the Knee](https://durgical.com/en/conditions/septic-arthritis-of-the-knee/)
- [Achilles Tendinopathy](https://durgical.com/en/conditions/achilles-tendinopathy/)
- [Plantar Fasciitis](https://durgical.com/en/conditions/plantar-fasciitis/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Reactive arthritis](https://medlineplus.gov/ency/article/000440.htm) (MedlinePlus (U.S. National Library of Medicine), 2025).

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Source: https://durgical.com/en/conditions/reactive-arthritis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/reactive-arthritis/