Can joint inflammation persist after Lyme arthritis without demonstrable ongoing infection?

After treated Lyme arthritis, persistent synovitis is a recognized post-antibiotic/postinfectious phenotype and is generally understood as immune-mediated rather than evidence of continuing viable Borrelia infection.

Clinical and pathological evidence

• Persistent arthritis can reflect active synovial inflammation, not simply lingering pain or structural damage. Reported synovial findings include hyperplasia, inflammatory-cell infiltration, vascular injury, fibroblast proliferation, and fibrosis.
• Post-treatment synovectomy specimens have reportedly been uniformly culture- and PCR-negative. Conversely, a positive synovial-fluid PCR shortly after treatment does not establish viable infection, because PCR detects Borrelia DNA, including DNA from killed organisms.
• This interpretation is reflected in guideline-supported practice: after adequate oral and intravenous antibiotic treatment, management may shift toward rheumatologic anti-inflammatory treatment—such as intra-articular corticosteroids, DMARDs, biologics, or, in selected cases, synovectomy—rather than prolonged antibiotics.

Immune mechanisms

• The leading model is persistent maladaptive synovial immunity, with an IFN-γ–high inflammatory response that is inadequately counterbalanced by IL-10-associated regulation.
• Studies also implicate altered regulatory T-cell function, IFN-γ-producing effector-like cells, cytotoxic CD8-positive and γδ T-cell populations, and possible autoreactive B-cell responses. Together, these mechanisms provide a biologically coherent explanation for inflammation continuing after bacterial clearance.
• Nonviable microbial remnants may still contribute to inflammatory signaling; this differs from demonstrating an ongoing viable infection.

Clinical interpretation

• Persistent or recurrent monoarthritis still warrants assessment for alternative explanations, particularly in an older adult, rather than assuming all joint symptoms represent post-antibiotic Lyme arthritis.

Bottom line

• The claim is well supported: following Lyme arthritis, joint inflammation can persist through immune-driven synovial pathology even when ongoing viable Borrelia infection cannot be demonstrated.