Elevated synovial fluid (SF) concentrations of proinflammatory cytokines, degradative enzymes, and cartilage
breakdown markers at the time of anterior cruciate ligament (ACL) reconstruction are associated with worse postoperative patient-reported outcomes and cartilage
quality. However, it remains unclear if this is due to a more robust or dysregulated inflammatory response or is a function of a more severe injury. The objective of this study was to evaluate the association of the molecular composition of the SF, patient demographics, and injury characteristics to cartilage
degradation after acute ACL injury.
We performed a cluster analysis of SF concentrations of proinflammatory and anti-inflammatory cytokines, and biomarkers of cartilage
degradation, bony remodeling, and hemarthrosis. We evaluated the association of biomarker
clusters with patient demographics, days between injury, Visual Analogue Scale pain, SF aspirate volumes, and bone bruise volumes measured on magnetic resonance imaging.
Two clusters were identified from the 35 patients included in this analysis, dysregulated inflammation
and low inflammation
. The dysregulated inflammation
cluster consisted of 10 patients and demonstrated significantly greater concentrations of biomarkers of cartilage
< 0.05) as well as a lower ratio of anti-inflammatory to proinflammatory cytokines (P
= 0.053) when compared with the low inflammation
cluster. Patient demographics, bone bruise volumes, SF aspirate volumes, pain, and concomitant injuries did not differ between clusters.
A subset of patients exhibited dysregulation of the inflammatory response after acute ACL injury which may increase the risk of posttraumatic osteoarthritis. This response does not appear to be a function of injury severity.