Reactive arthritis ("Reiter's") follows about 1% of chlamydia infections. The triad — joint pain, eye irritation, urethral symptoms — can persist for months. Here's the practical guide.

Reactive Arthritis from STIs (Reiter's Syndrome) — What to Know

Reactive arthritis — sometimes still called Reiter's syndrome — is a post-infectious autoimmune condition that can follow chlamydia, gonorrhea, or some gastrointestinal infections. The classic triad is joint pain, eye inflammation, and urethral symptoms. It affects about 1% of chlamydia infections.

It's manageable but often misdiagnosed. Here's the practical picture.

The short answer

What it is: Joint inflammation triggered by recent infection (usually 1-4 weeks after)
Common triggers: Chlamydia, gonorrhea, Salmonella, Shigella, Campylobacter
Classic triad: Joint pain + eye inflammation + urethritis
Genetics matter: HLA-B27 genetic marker increases risk
Treatment: Treat underlying infection + NSAIDs + sometimes longer-term immunomodulators
Duration: Most resolve in 3-12 months; some become chronic

What it looks like

The classic triad

Arthritis — pain, swelling, stiffness in joints (most commonly knees, ankles, feet)
Conjunctivitis or uveitis — red, painful eye(s)
Urethritis — burning with urination, discharge (in cases triggered by chlamydia/gonorrhea)

You don't need all three for diagnosis — and many cases don't have all three.

Joint involvement details

Usually asymmetric (different in each side of body)
Affects lower extremities most often (knees, ankles, feet)
Heels and tendons commonly involved (enthesitis)
Sometimes sacroiliac joints (lower back)
Pain often worse at rest, better with activity
Joints feel hot, swollen, painful

Skin/nail involvement (less common)

Keratoderma blennorrhagicum — pustular skin lesions on palms/soles
Circinate balanitis — ring-like rash on glans penis
Nail changes similar to psoriasis

Mouth/oral involvement

Painless ulcers in mouth
Sometimes silvery patches on tongue

Who gets it

Risk factors

HLA-B27 genetic marker — 50-80% of patients have it (5-8% of general population)
Male sex — 9:1 in chlamydia-triggered cases
Age 20-40 typically
Recent STI or GI infection

Triggers (in order)

Chlamydia trachomatis — most common STI trigger
Gonorrhea — less common but possible
Salmonella — common GI trigger
Shigella — GI trigger
Campylobacter — GI trigger
Yersinia — GI trigger
C. difficile — rare trigger
COVID-19 — recently recognized trigger

How it develops

Timeline

Triggering infection: now or 1-4 weeks ago
Joint symptoms: appear 1-4 weeks after triggering infection
Eye and skin symptoms: variable timing
Course: usually 3-12 months; can be chronic

Mechanism

Triggering infection elsewhere causes immune response
Some bacterial fragments may persist in joints
Genetic predisposition (HLA-B27) makes immune system overreact
Autoimmune attack on joints, eyes, skin

Diagnosis

Clinical features

New asymmetric arthritis in lower extremities
Recent STI or GI infection (asked about)
Compatible eye findings
Urinary or skin symptoms

Lab tests

HLA-B27 testing — positive in 50-80% of patients
Inflammatory markers (ESR, CRP) — usually elevated
STI testing — chlamydia, gonorrhea NAAT
Joint fluid analysis if joint is aspirated
Cultures for any current infection
Negative rheumatoid factor (distinguishes from rheumatoid arthritis)

Imaging

X-rays — sometimes show inflammation
MRI — better at showing early inflammation
Ultrasound — for tendon involvement (enthesitis)

Differential diagnosis

Septic arthritis — true joint infection (urgent, requires drainage)
Rheumatoid arthritis — chronic, symmetric, RF+
Psoriatic arthritis — with skin psoriasis
Ankylosing spondylitis — different pattern
Lyme disease — with appropriate exposure
Gout — uric acid crystals
Disseminated gonococcal infection — bacteria in joint

Treatment

Treat the triggering infection

If chlamydia: doxycycline 100 mg twice daily for 7 days
If gonorrhea: ceftriaxone 500 mg IM
If still present: targeted antibiotics
See chlamydia symptoms in men and similar

NSAIDs for joint symptoms

Ibuprofen, naproxen, indomethacin are first-line
Reduce inflammation and pain
Continue for weeks to months
Watch for GI side effects, kidney function

Corticosteroids

For severe cases not responding to NSAIDs
Joint injections for severely affected single joints
Oral if multiple joints
Tapered carefully

DMARDs (disease-modifying antirheumatic drugs)

For chronic or severe cases
Sulfasalazine, methotrexate sometimes used
Slower-acting; long-term medication

Biologics

For refractory chronic cases
TNF inhibitors (etanercept, adalimumab)
Specialty rheumatology care needed

Physical therapy

Maintain joint range of motion
Strengthen surrounding muscles
Prevent stiffness
Often very helpful

Eye involvement

Conjunctivitis

Red, irritated eyes
Discharge
Mild treatment: lubricating drops, sometimes antibiotic drops
Usually self-limited

Uveitis

Inflammation of internal eye structures
More serious; can cause vision damage
Requires urgent ophthalmology evaluation
Treatment: topical corticosteroids, dilating drops
Sometimes oral or injectable corticosteroids

Prognosis

Short-term

Acute episode usually 3-12 months
Symptom severity varies widely
Most can return to normal activities with treatment

Long-term

About 50% resolve completely
30-50% have intermittent flares
15-30% develop chronic disease
5-15% develop joint damage

Factors predicting worse outcome

HLA-B27 positive
Male sex
Hip joint involvement
Severe initial disease
Chronic course beyond 12 months

Partner considerations

If STI-triggered

Treat the partner for the triggering STI
They may also develop reactive arthritis (low risk, but possible)
Standard STI counseling

Sexual activity during reactive arthritis

After completion of antibiotic treatment for triggering STI
After resolution of urethral symptoms
Joint symptoms don't preclude sex

Recurrence prevention

After acute episode

Avoid future trigger infections when possible (STI prevention, food safety)
Genetic counseling if HLA-B27 positive
Awareness of early symptoms
Quick treatment of any infection

Long-term management

Annual rheumatology follow-up if chronic
Eye checks if previous uveitis
Maintain physical activity
Address mental health (chronic illness is hard)

Special situations

HIV+ patients

Reactive arthritis can be more severe
Different treatment approaches may be needed
Coordinate with HIV care provider

Pregnancy

Reactive arthritis in pregnancy is uncommon
Treatment usually NSAIDs (avoid in late pregnancy)
Some medications contraindicated
Specialty care needed

Pediatric cases

Different presentation
Different triggers (often viral or GI)
Different treatment approach

Why reactive arthritis matters

Often missed

Symptoms attributed to "I worked out too hard" or "got the flu"
STI history not asked about
Eye symptoms attributed to other things
Misdiagnosed as gout, rheumatoid arthritis, or septic arthritis

Knowing it exists

Helps quicker diagnosis
Earlier treatment
Better long-term outcomes
Less anxiety about mysterious illness

When to see a doctor

New joint pain + swelling without injury
Joint pain + eye redness
Joint pain + urinary symptoms
Joint pain + recent diarrhea
Joint pain + recent STI exposure or diagnosis

Which specialist

Primary care for initial evaluation
Rheumatologist for confirmation and management
Ophthalmologist if eye involvement
Urology if persistent urinary symptoms

Common confusions

"It's just arthritis from getting older." Reactive arthritis affects young adults specifically.

"I had food poisoning a month ago — couldn't be related." Actually, this is exactly the typical pattern.

"My chlamydia was treated — why are my joints hurting?" Treatment kills the infection, but immune response continues. Reactive arthritis can develop after the infection is gone.

"Why am I HLA-B27 positive — does that mean I'm sick?" No. HLA-B27 is just a genetic marker. Most people with it never have problems. It increases risk of reactive arthritis specifically.

"Is reactive arthritis contagious?" No — the immune response is yours. Only the triggering infection is contagious.

Bottom line

Reactive arthritis is:

A post-infectious autoimmune syndrome following chlamydia, gonorrhea, or GI infections
Triad of joint pain + eye inflammation + urethral symptoms (classic, not always present)
More common in HLA-B27 positive young men
Treatable with NSAIDs + treating triggering infection
Most resolve in 3-12 months — but chronic cases occur
Important to recognize for proper treatment

If you have unexplained joint pain after recent infection (STI or GI), reactive arthritis is on the differential. Your provider may not think of it first — bring it up.