Inflammatory markers in early knee joint osteoarthritis differ from well-matched controls and are associated with consistent, rather than intermittent knee pain.

Background: Osteoarthritis (OA) is characterised by the failure of normal biological processes to repair following damage. Traditionally, OA was considered a "wear and tear" disorder; however, it is now a recognised inflammatory condition, preceded by molecular modifications. The aim of this study was to evaluate inflammatory markers among individuals with early knee OA (eKOA) and well-matched asymptomatic controls.
Methods: Twenty six eKOA (females, n = 13; age = 60.2 ± 5.4 yrs, height = 1.73 ± 0.11 m, body mass = 77.8 ± 12.8 kg, body fat = 33.9 ± 8.5%) and twenty-three asymptomatic individuals (females, n = 14; age = 59.9 ± 5.5yrs, height = 1.71 ± 0.09 m, body mass = 72.6 ± 11.3 kg, body fat = 30.4 ± 8.2%) were recruited. The Timed Up and Go, and the 6 Minute Walk Tests evaluated physical function in addition to pain specific questionnaires (KOOS and ICOAP). Serum levels of IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8(CXCL8), IL-10, hsCRP and TNF-α were quantified using a multiplex assay via V-plex®Sector Imager 2400.
Results: As hypothesised, only KOOS and EQ-5D-5L metrics differed between the groups for non-blood derived measures (p < 0.04). Only IL-6 was higher in eKOA (P = 0.02; 95% CI = 0.202; by 0.197 pg/mL; 34.5%). Among eKOA, IL-6 did not relate to severity of KOOS pain (P = 0.696, r = -0.088), but had a positive relationship with ICOAP consistent (r = 0.469, P = 0.045) rather than intermittent pain. There was a moderate correlation between 6MWD and IL-8 (r = 0.471, P = 0.012).
Conclusion: Our results illustrate the potential for IL-6 as a biomarker for eKOA, and introduce the proposition for particular consideration in those with consistent pain. Further, for the first time the present data showed greater walking distance in eKOA with lower circulating IL-8. Future work should seek to verify these results and further investigate IL-6 and IL-8 related molecular pathways in eKOA, and their potential relationships with consistent knee pain and physical function.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)