Distinct Synovial Fluid Microbiome Profiles in Primary Anterior Cruciate Ligament Repair Versus Total Knee Arthroplasty Patients Without Recent Intra-Articular Injections- Madigan Research Day 2026

M Deegan, B Kowalski, R Frenette, F say, L Gillette, Z Colburn, J Dannenbaum, M Bedrin

Abstract accepted for poster presentation at Madigan Research Day 2026

Background: The synovial fluid microbiome is becoming increasingly recognized for its role in joint health and disease, yet how its composition differs relates to different joint conditions such as in patients undergoing primary anterior cruciate ligament (ACL) repair and total knee arthroplasty (TKA) remains poorly characterized. We aimed to compare synovial fluid microbiome profiles between these two distinct patient groups.

Methods: Synovial fluid samples were collected from 13 ACL patients and 13 TKA patients during surgery. Microbial DNA was extracted and analyzed using 16S rRNA gene sequencing targeting the V3-V4 hypervariable regions. Bioinformatics analysis was performed using QIIME 2, and microbial diversity metrics were calculated. Statistical comparisons of demographic attributes, alpha diversity indices, and differential abundance of microbial taxa were conducted.

Results: Significant demographic differences were observed between the groups, with ACL patients being younger (median age: 25 years) and predominantly male, while TKA patients were older (median age: 67 years) and exclusively female. Alpha diversity metrics revealed significantly higher microbial richness and evenness in TKA patients compared to ACL patients, as evidenced by Chao1, Shannon, and Inverse Simpson indices. Differential abundance analysis identified several taxa enriched in TKA patients, including Burkholderia, Aquabacterium, and Moraxella cinereus, while taxa such as Acinetobacter proteolyticus and Pseudomonas alloputida were more abundant in ACL patients.

Conclusion: Our results reveal distinct synovial fluid microbiome profiles between ACL and TKA patients, with significant differences in microbial diversity and taxa abundance. These findings provide insights into the potential role of the microbiome in joint health and recovery, paving the way for future research on microbiome-targeted therapies in orthopaedic care.