Abstract / Summary
Abstract The concept of a native intra-articular knee microbiome has gained attention, challenging the traditional belief that the synovial joint is sterile. Advances in next-generation sequencing (NGS) and metagenomic analysis have revealed microbial communities within synovial fluid and joint tissues, raising questions about their role in joint health and disease. Potential sources of microbial colonization include hematogenous dissemination, local translocation, or introduction through trauma or surgery. Dysbiosis may contribute to osteoarthritis (OA) and inflammatory joint disorders by promoting chronic inflammation, increasing pro-inflammatory cytokines, and accelerating cartilage degradation. Differentiating between commensal microbiota and infection is clinically important to avoid misinterpretation and overtreatment. This narrative review was based on a comprehensive literature search of PubMed, Scopus, Web of Science, and Google Scholar for English-language articles published between January 2010 and March 2025. Search terms included “knee microbiome,” “synovial fluid,” “intra-articular bacteria,” and “metagenomic analysis of joints.” Eligible studies included original research, systematic reviews, and preclinical studies focused on microbial presence, composition, or clinical relevance in the knee joint. Studies employing NGS, 16S rRNA analysis, or metagenomic methods were prioritized. Current challenges include distinguishing true microbial colonization from contamination, lack of standardized protocols, and limited longitudinal data. Understanding the knee microbiome could transform diagnostic and therapeutic approaches in joint diseases. Future research should aim to clarify host-microbe interactions, establish reliable detection methods, and explore microbiome-targeted therapies for OA and other joint pathologies.