OBJECTIVE

To assess the relation between microbiome and lipopolysaccharide (LPS), in the blood and synovial fluid (SF) with femoral cartilage thickness (FCT) measured by ultrasound (US) in knee osteoarthritis (KOA) patients.

METHODS

This cross-sectional study included 40 primary KOA patients recruited between September 2022 and June 2023. Age, gender, and body mass index (BMI) were recorded. Patients underwent full clinical examination, standing plain x-ray of the knee joint and knee US examination to measure medial, intercondylar, and lateral FCT. Microbiomes (specific bacterial phyla) were detected by real-time polymerase chain reaction and LPS levels were measured by enzyme-linked immunosorbent assay kit in the patients' serum and SF.

RESULTS

The patient's age ranged from 43 to 72 years. Most patients were females (72.5%), with a mean BMI of 35.8 ± 6.21 kg/m. The mean medial, intercondylar, and lateral FCT were less than cut-off values. All 40 (100%) patients showed positive bacterial deoxyribonucleic acid (16S ribosomal RNA) in both blood and SF samples. was the most abundant in patients' blood (48.49%) and SF (63.59%). The mean serum LPS level was significantly higher compared to mean SF LPS ( =4.702, < 0.001). There was a statistically significant negative correlation between lateral FCT and relative abundance in both patients' blood and SF.

CONCLUSION

Microbiome and LPS are present in the blood and SF of primary KOA patients. Microbiome () was associated with decreased lateral FCT. This might provide a potential link between both systemic and local microbiomes and cartilage affection in KOA patients.