A cross-sectional exploratory study of synovial fluid complement levels and ultrasound-assessed structural damage in patients with symptomatic knee osteoarthritis and synovial effusion
Year: 2026
Type: article
Study design: Observational Study
Abstract: Background Knee osteoarthritis (KOA) is characterised by low-grade inflammation in which the innate immune system, particularly the complement cascade, plays a crucial role. The aim of this study was to evaluate the correlation between synovial fluid (SF) complement levels (C3 and C4) and structural joint damage assessed by ultrasound (US) in patients with KOA. Methods A cross-sectional study was conducted including 31 patients with symptomatic KOA and joint effusion. US assessment was performed according to OMERACT criteria, including grading of synovitis, osteophytes, meniscal involvement and cartilage degradation. C3 and C4 levels in SF were measured using turbidimetric techniques. Results Synovial fluid C3 levels showed a significant inverse association with structural damage. Lower C3 levels were associated with higher grades of osteophytosis (p = 0.015), meniscal pathology (p = 0.031), and cartilage degradation (p = 0.049). No significant associations were found between synovitis grades and SF C3 and C4 levels. Conclusions SF C3 levels are inversely associated with ultrasound-detected structural damage in KOA, suggesting increased complement activation in early disease stages. C3 may serve as a potential biomarker of disease activity. Trial Registration The methodology of this study has been evaluated and approved by the Ethics Committee for Clinical Research (Granada, Spain). (Registration number SICEIA2024001805).
Source: BMC Musculoskeletal Disorders
Institution: Universidad de Granada
Language: English
Subfield: Rheumatology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,090
OpenAlex ID: W7203796725