For the roughly one in ten total knee replacement patients who leave surgery no better off despite technically flawless outcomes, the absence of any objective pain measurement has long been a clinical blind spot. If peripheral immune signals could reliably quantify pain severity, surgeons and pain specialists would gain a tool that subjective rating scales simply cannot provide — potentially transforming patient selection, postoperative care, and satisfaction rates.
This registered protocol describes a prospective, cross-sectional, matched-subject observational study based at a South Australian tertiary center. The central hypothesis is that interleukin-1 beta (IL-1β), a pro-inflammatory cytokine involved in peripheral immune signaling, may track meaningfully with self-reported pain intensity in adults with advanced knee osteoarthritis awaiting total knee arthroplasty. The design recruits 20 surgical candidates alongside their own contralateral pain-free knees as internal controls and 20 age- and sex-matched healthy controls — a compact but methodologically elegant three-way comparison. Crucially, IL-1β measurements will be correlated not only with pain scores but also with validated psychological patient-reported outcome measures capturing anxiety, depression, and pain catastrophizing, acknowledging the well-documented psychosocial modulation of chronic pain perception.
The neuroimmune interface in musculoskeletal pain has received growing scientific attention over the past decade, with IL-1β in particular implicated in central sensitization and synovial inflammation. However, this proposed study is, by the investigators' own account, the first to directly correlate peripheral immune markers with subjective pain in this orthopaedic population. That framing deserves measured scrutiny: the sample size of 20 patients is modest and appropriate for a hypothesis-generating pilot, but far too small to establish clinical diagnostic thresholds or validate a biomarker for routine practice. As a protocol publication, no outcome data yet exist. The observational, cross-sectional architecture also precludes causal inference. If IL-1β associations with pain scores prove robust in this pilot, they would warrant replication in much larger, longitudinal cohorts before any clinical translation could be responsibly considered. Incrementally, this study occupies a useful early rung — establishing feasibility and generating effect-size estimates for future powered trials.