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

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.

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.

Cohort study; Level of evidence, 3.

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.

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.

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.