Abstract Background Lyme arthritis is the most common late manifestation of disseminated Lyme disease in the United States. While most patients respond to antibiotic therapy, a subset develops post-antibiotic Lyme arthritis (PALA), characterized by persistent non-infectious inflammatory arthritis. Data describing predictors of PALA and treatment patterns remain limited. Methods We conducted a retrospective observational cohort study of patients with polymerase chain reaction (PCR)–confirmed native joint Lyme arthritis treated at our institution from 2004-2025. Clinical, laboratory, imaging, treatment, and outcome data were abstracted from electronic health records. Continuous variables were compared using the Mann–Whitney U test, and categorical variables using Fisher’s exact test. Results Seventy-seven patients with PCR-confirmed native joint Lyme arthritis were identified: 64 adults and 13 children. Children more frequently presented with fever and had significantly higher synovial fluid white blood cell counts compared with adults. Knee monoarthritis was the predominant presentation in both groups. Among adults, 41 (64%) achieved complete symptomatic resolution following antibiotic therapy, while 19 (29.7%) developed PALA. Adults who developed PALA had significantly lower synovial fluid white blood cell counts and more extensive joint involvement. Use of intravenous antibiotics and longer total antibiotic duration was more common among PALA patients without evidence of improved outcomes. Conclusions In this cohort of PCR-confirmed native joint Lyme arthritis, a substantial proportion of adults developed PALA. Failure to respond to initial antibiotic therapy and certain clinical features may identify patients at increased risk. These findings support judicious antibiotic use and early consideration of non-infectious mechanisms in persistent arthritis.
Abu-Zeinah et al. (Wed,) studied this question.