Lyme Arthritis – When Joint Swelling Follows a Tick Bite

A tick bite is easy to miss. Sometimes there’s no pain, and the tick goes unnoticed for days. But weeks or even months later, a child may suddenly develop a swollen, painful knee—without fever or other signs of illness. In such cases, Lyme arthritis may be the hidden cause.

This form of joint inflammation is a late complication of Lyme disease, and recognizing it is key to getting the right treatment—and avoiding unnecessary worry.

⚠️ Important: If your child develops persistent swelling in one or more joints, especially the knees, and has a history of tick exposure (even months earlier), Lyme arthritis should be considered. Talk to your pediatrician or pediatric rheumatologist about testing and treatment.

What Is Lyme Arthritis?

Lyme arthritis is a complication of Lyme disease, which is caused by the bacterium Borrelia burgdorferi, transmitted through tick bites. While the early stage of Lyme disease often includes a rash (such as erythema migrans), flu-like symptoms, or fever, Lyme arthritis can appear weeks or months later, even if those early signs were missed or mild.

What Are the Symptoms?

The most common features of Lyme arthritis are:

• Swelling in one or more joints, most often the knees

• The joint may be painless or only mildly painful, despite being visibly enlarged

• Limited movement or stiffness in the joint

• Sometimes swelling comes and goes over several weeks

• Usually no fever or general illness at the time of arthritis onset

Some children may have had a previous tick bite, rash, or flu-like illness—but not always.

How Is It Diagnosed?

Diagnosis is based on:

• History of tick exposure or travel to a Lyme-endemic area

• Clinical signs (especially monoarthritis of the knee)

• Blood tests for Lyme antibodies (ELISA and confirmatory Western blot)

• Joint fluid analysis (sometimes needed to rule out other causes)

Other forms of arthritis (e.g. juvenile idiopathic arthritis) may look similar, so testing is important.

How Is It Treated?

Lyme arthritis is treated with antibiotics, usually for 2 to 4 weeks. The most commonly used are:

• Amoxicillin or doxycycline (age-dependent)

• Cefuroxime in some cases

• IV antibiotics only if the condition is resistant or complications arise

Anti-inflammatory medications (like NSAIDs) may also help relieve symptoms. In rare cases, if arthritis persists after antibiotics, short-term DMARDs or biologics may be considered in consultation with a pediatric rheumatologist.

What’s the Outlook?

Most children with Lyme arthritis recover completely after antibiotic treatment, even if joint swelling takes a few weeks to resolve. Early recognition avoids unnecessary tests, delays, or use of strong medications.

Preventing tick bites and recognizing the early signs of Lyme disease remain key.

Learn More

PRINTO provides a clear and concise leaflet on Lyme arthritis for families and caregivers.

🔗 Read more on PRINTO:

Lyme Arthritis – PRINTO Patient Leaflet

All rights and content remain with PRINTO, and the original resources can be found at:

https://www.printo.it/pediatric-rheumatology/GB/info/GB