Papers of the Week

Anterior cruciate ligament (ACL) injury initiates a biochemical cascade thought to contribute to the onset and progression of posttraumatic osteoarthritis (PTOA). Interleukin-1ß (IL-1ß), IL-6, and C-telopeptide fragments of type II collagen (CTX-II) are implicated in joint inflammation and cartilage degradation following ACL injury; however, their association with pain is still being explored. The purpose of this study was to evaluate the associations between synovial fluid concentrations of IL-1ß, IL-6, and CTX-II with pain following ACL injury and reconstruction. We hypothesized that greater IL-1ß, IL-6, and CTX-II would correlate with greater Pain Visual Analogue Scale (VAS) scores. This was a secondary analysis of 23 patients (mean age=18.4 y, BMI=27.4, 13 Females/10 Males) with acute ACL tears who participated in a pilot randomized trial. Synovial fluid and VAS scores were collected on the day of initial presentation, at ACL reconstruction, and 1- and 4-weeks after surgery. Synovial fluid concentrations of IL-1ß, IL-6, and CTX-II were assessed using enzyme linked immunoabsorbent assays (ELISA), and repeated measures correlations were used to assess the relationships between pain and synovial IL-1ß, IL-6, or CTX-II after ACL injury and reconstruction. Pain was positively correlated with synovial fluid IL-6 concentrations (r=0.52, p<0.001); however, pain was inversely correlated with CTX-II (r= -0.39, p=0.002). IL-1ß had no significant correlation with pain. Statement of Clinical Relevance PTOA has been described as a "silent killer" and these results suggest that early PTOA may have pro-inflammatory pathways that are not primarily associated with pain but still lead to progressive cartilage loss. This article is protected by copyright. All rights reserved.