Purpose

Injuries of the meniscus and ACL cause disrupted mechanics, intra-articular inflammation, and degenerative joint disease. Synovial fluid biomarkers have the potential to reflect this intra-articular environment and predict which patients are at risk for poor outcomes. The current study aims to establish how synovial fluid biomarker concentrations are dependent on the chronicity of preoperative symptoms.

Methods and Materials

Patients undergoing arthroscopy for meniscal and/or ACL tears were prospectively enrolled. Synovial fluid samples were obtained immediately prior to surgical incision. The concentrations of ten pro- and anti-inflammatory cytokines, chemokines, and growth factors were measured using ultra-sensitive kits.

Results

There were 275 patients (mean age 41.73 +/- 13.9 years) included in the study. Forty-three (15.6%) underwent ACL reconstruction alone, 145 (52.7%) underwent isolated meniscal repair or meniscectomy, and 87 (31.6%) had both. The mean duration of isolated symptomatic ACL or meniscal tears were 2.77 and 12.8 months, respectively, while the mean duration of symptomatic combined ACL and meniscal tears was 5.2 months.

When the duration of pre-operative symptoms increased, there was a decrease in the concentration of four of the five pro-inflammatory biomarkers. As the duration of symptoms increased, there were also decreases in the concentrations of the anti-inflammatory biomarker IL-1Ra and the growth factor VEGF. For every 10% increase in the chronicity of the injury, there was 4.7% decrease in IL-6 concentration, 1.2% decrease in MCP-1 concentration, 0.9% decrease in MIP-1β concentration, 3.6% decrease in MMP-3 concentration, 1.6% decrease in IL-1Ra concentration, and 2.5% decrease in VEGF concentration.

Conclusion

The current study identified a significant negative correlation between the chronicity of knee pathology and the concentration of several known pro- and anti-inflammatory cytokines. Long-term studies in this patient cohort will help determine if abnormalities from the baseline are associated with the development of progressive degenerative changes in the knee.