Cale A. Jacobs

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 years, 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, 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.