Impact of Pre-Operative Intra-Articular Injections on Synovial Fluid Microbiome Composition in Total Knee Arthroplasty Patients- Madigan Research Day 2026

C Gerber, M Feldman, R Frenette, F Say, L Gilette, Z Colburn, J Dannenbaum, M Bedrin

Abstract accepted for poster presentation at Madigan Research Day 2026

Background: Intra-articular injections are commonly administered prior to total knee arthroplasty (TKA) to manage pain and inflammation, yet their impact on the synovial fluid microbiome remains unclear. We aimed to investigate the influence of pre-operative intra-articular injections on the synovial fluid microbiome composition in TKA patients.

Methods: Twenty-six TKA patients were divided into two cohorts: those who received an intra-articular injection within six months prior to surgery (injection group, n=13) and those who did not (non-injection group, n=13). Synovial fluid samples were collected during surgery, and microbial DNA was extracted for 16S rRNA gene sequencing targeting the V3-V4 hypervariable regions. Bioinformatics analysis was performed using QIIME 2, and microbial diversity metrics and differential abundance of taxa were compared.

Results: Demographic comparisons revealed significant differences in sex distribution and beneficiary category between the injection and non-injection groups, while age, race, and ethnicity showed no significant differences. Alpha diversity metrics, including Chao1, Shannon, Inverse Simpson, and Fisher's alpha, demonstrated no statistically significant differences between the two groups. However, differential abundance analysis identified several microbial taxa with significantly altered relative abundances between the injection and non-injection groups. Specifically, 30 taxa were enriched in the injection group, while 16 taxa were more abundant in the non-injection group.

Conclusion: We identified specific differences in the synovial fluid microbiome associated with pre-operative intra-articular injections in TKA patients. These findings provide insights into the potential microbiome-related effects of intra-articular injections, paving the way for further research on their implications for joint health and surgical outcomes.