Proinflammatory Synovial Fluid Biomarkers Predict Poor Long-term Outcomes in Chronic Meniscal Injuries

Background: Synovial fluid (SF) biomarkers demonstrate time-dependent variation after acute knee injury, and it is postulated that persistently elevated inflammatory markers may mediate worse long-term outcomes. Purpose: This study investigated the relationship between biomarkers in SF at the time of meniscectomy and long-term patient-reported outcomes in patients with acute versus chronic meniscal injuries. Study Design: Cohort study; Level of evidence, 3. Methods: This retrospective analysis included patients who underwent knee SF aspiration on the day of arthroscopic meniscectomy between October 2011 and October 2020 with minimum 4-year follow-up. SF aspirated from the operative knee was analyzed for 10 pro- and anti-inflammatory biomarkers. Patients completed the visual analog scale for pain, Lysholm Knee Questionnaire, Tegner Activity Scale, and Knee injury and Osteoarthritis Outcome Score–Physical Function Short-form (KOOS-PS) before surgery and at follow-up. Patients were categorized as having acute (<6 weeks) or chronic (>1 year) symptoms. K-means clustering analysis was performed using biomarker levels to group patients into distinct cohorts. Results: Of 85 patients meeting inclusion criteria, 55 had chronic and 30 had acute meniscal pathology, with 62 (72.9%) completing patient-reported outcome surveys at a mean follow-up of 8.66 years (SD, 2.27). K-means clustering identified 2 distinct biomarker profiles: a high-inflammation cluster and a low-inflammation cluster. The high-inflammation cluster had higher levels of 7 proinflammatory biomarkers as compared with the low-inflammation cluster ( P = .015). The low-inflammation cluster predominantly comprised chronic meniscal injuries (89.2%), whereas the high-inflammation cluster was divided between acute and chronic cases. There were no differences in postoperative outcomes between clusters in the overall cohort. However, within the chronic cohort, the high-inflammation cluster exhibited worse postoperative scores on the visual analog scale for pain ( P = .035), Lysholm questionnaire ( P = .007), KOOS-PS ( P = .038), and Tegner scale ( P = .049) and had a higher rate of postoperative injections ( P = .020) than the low-inflammation cohort. Conclusion: In patients with chronic meniscal injury, those with a more proinflammatory SF biomarker profile at the time of meniscectomy had worse outcomes than those who had a low inflammatory profile. In acute meniscal injuries, most patients demonstrate a high inflammatory profile, which was not associated with a difference in long-term outcomes.