Effect of Cartilage Lesions on the Metabolic Profiles of Synovial Fluid in Patients With Anterior Cruciate Ligament Tears

Background: Anterior cruciate ligament (ACL) tears often coincide with variable extents of cartilage lesions, which typically worsen clinical symptoms and increase osteoarthritis risk. Alterations in the metabolic profile may be informative for the response of the ACL-injured knee to cartilage lesions. Purpose: To determine the effect of the severity of cartilage lesions on synovial fluid metabolism of patients with ACL tears by (1) identifying characteristic metabolites and key metabolic pathways and (2) analyzing the associations between these biomarkers and patient-reported outcome measures (PROMs). Study Design: Cross-sectional study; Level of evidence, 4. Methods: Synovial fluid was extracted from 39 patients with ACL tears and various severity of cartilage lesions. According to the Outerbridge classification system, patients were divided into high- and low-grade cartilage lesion groups. The metabolic profiles of the synovial fluid were evaluated by ultraperformance liquid chromatography–mass spectrometry, and the differences between the groups were calculated. Pearson correlation analysis examined the correlation between metabolic differences and PROMs. Results: A total of 34 metabolites showed differences between the groups, mainly involved in 9 key pathways. Among them, oleoylethanolamide, 13-hydroxyoctadecadienoic acid, glucose, and 5-hydroxylysine are implicated in Lysholm and International Knee Documentation Committee scores. Conclusion: The severity of cartilage injury has a significant metabolic effect on the synovial fluid of knees with ACL tears, which correlates with PROMs and may provide new insights into the pathogenesis of osteoarthritis. Registration: ChiCTR220061779 (Chinese Clinical Trial Registry).