Definition
A tick borne infection by Borrelia burgdorferi sensu lato. Lyme arthritis is the late stage, a mono or oligoarthritis of large joints.
Epidemiology
- Transmitted by Ixodes ticks in endemic parts of North America, Europe and Asia
- Highest incidence in the northeastern United States and central Europe
- Arthritis is more frequent with North American strains
Clinical Features
- Early localised disease with erythema migrans at the bite site within 30 days
- Early disseminated disease with carditis, heart block, facial palsy and meningitis
- Late disease with arthritis months after the bite
- Knee involved in most cases, with a large tense effusion
- Effusion often larger and less painful than in septic arthritis
- Children may present with an irritable hip or knee
Investigations
- Two tier serology, an ELISA followed by Western blot or a second immunoassay
- IgG serology is positive in nearly all patients with arthritis
- Synovial PCR for Borrelia DNA supports the diagnosis
- Synovial leucocytes usually lower than in septic arthritis
- Kocher criteria may misclassify Lyme arthritis as septic in endemic areas
Differential Diagnosis
- Septic arthritis
- Septic arthritis in children
- Reactive arthritis
- Juvenile chronic arthritis
- Transient synovitis of the hip
Management
- Doxycycline. 28 days orally for Lyme arthritis
- Amoxicillin. 28 days orally in young children or pregnancy
- Intravenous ceftriaxone. 2 to 4 weeks for persistent arthritis after oral therapy
- DMARDs or synovectomy. Postinfectious synovitis that persists after antibiotics
Prognosis
- Most cases resolve with antibiotics
- Antibiotic refractory arthritis in a minority, linked to HLA-DR4
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 19 October 2026.