Published: 18 Jun 2025

ICD9: 711.17      ICD10: M02.379      ICD11: FA11.2

Reactive arthritis (ReA), also known as post-infectious arthritis, is a type of arthritis that develops as a reaction to an infection in the body, often in the genitourinary or gastrointestinal tract.
It's an autoimmune condition, meaning the body's immune system mistakenly attacks healthy tissues after fighting off the infection.

Here's a breakdown of the key aspects:

Key Characteristics:

Follows an Infection: The most defining feature. Arthritis develops after an infection, usually a few weeks to a month.
No Bacteria Present in the Joint: Unlike septic arthritis, there are no bacteria directly invading the affected joint. The arthritis is a *reaction* to an infection elsewhere.
Asymmetric Arthritis: It tends to affect large joints, especially those in the lower body like knees, ankles, and feet, but often in an asymmetrical pattern (one side more affected than the other).
Extra-Articular Symptoms: ReA often involves symptoms beyond the joints, including:
Uveitis (inflammation of the eye): Causes redness, pain, and blurred vision.
Urethritis (inflammation of the urethra): Causes pain or burning during urination.
Conjunctivitis (inflammation of the conjunctiva): Causes redness and discharge in the eye.
Skin rashes: Such as keratoderma blennorrhagicum (painless, waxy lesions on the palms and soles) or circinate balanitis (small, painless lesions on the penis).
Mouth sores (oral ulcers): Typically painless.
Enthesitis: Inflammation where tendons and ligaments attach to bone, particularly at the heel (Achilles tendon) or plantar fascia.

Common Triggering Infections:

Genitourinary Infections:
*Chlamydia trachomatis* (most common)
Gastrointestinal Infections:
*Salmonella*
*Shigella*
*Yersinia*
*Campylobacter*
*Clostridium difficile* (less common)

"Can't See, Can't Pee, Can't Climb a Tree":

This is a classic (but not always present) triad of symptoms that helps remember the key features:

Can't See: Uveitis/Conjunctivitis (eye inflammation)
Can't Pee: Urethritis (inflammation of the urethra)
Can't Climb a Tree: Arthritis (joint pain and stiffness, particularly in the lower extremities)

Who Gets Reactive Arthritis?

Age: Most common in young adults (20-40 years old).
Gender: Genitourinary-related ReA is more common in men. Gastrointestinal-related ReA affects men and women equally.
Genetic Predisposition: Individuals with the HLA-B27 gene are at a higher risk of developing reactive arthritis, especially after *Chlamydia* infection. However, not everyone with HLA-B27 develops the condition.

Diagnosis:

Clinical Evaluation: Based on symptoms, physical exam, and history of a preceding infection.
Blood Tests:
Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are often elevated, indicating inflammation.
HLA-B27 testing (though not diagnostic, it can support the diagnosis).
Testing for recent infections (e.g., *Chlamydia* PCR, stool cultures).
Joint Fluid Analysis: To rule out septic arthritis (bacterial infection directly in the joint). In ReA, the fluid will be inflammatory but without bacteria.
Imaging (X-rays, MRI): Can show signs of joint inflammation and damage, especially in chronic cases.

Treatment:

The goals of treatment are to:

Treat the underlying infection: Antibiotics for *Chlamydia* or other identified infections.
Relieve pain and inflammation:
NSAIDs (nonsteroidal anti-inflammatory drugs) like ibuprofen or naproxen.
Corticosteroids (oral or injected into the joint) for more severe inflammation.
Disease-modifying antirheumatic drugs (DMARDs) like sulfasalazine or methotrexate may be used for chronic or persistent arthritis.
Manage extra-articular symptoms:
Eye drops for uveitis/conjunctivitis.
Topical creams for skin rashes.
Physical therapy: To maintain joint mobility and strength.

Prognosis:

Most cases of reactive arthritis are self-limiting, resolving within a few months to a year.
However, some individuals develop chronic arthritis that requires ongoing treatment.
Recurrences are possible, especially after subsequent infections.

In summary, reactive arthritis is a complex inflammatory condition that arises as a reaction to an infection, causing arthritis and often other symptoms like eye inflammation and urinary tract issues. Early diagnosis and treatment can help manage symptoms and prevent long-term complications.

It is important to consult with a healthcare professional for proper diagnosis and treatment if you suspect you have reactive arthritis.