Background: C-reactive protein (CRP) is a well-established marker of systemic inflammation, while Growth Differentiation Factor-15 (GDF-15) has emerged as a potential biomarker of cellular stress. Their relative perioperative dynamics remain incompletely defined.

This prospective observational study aimed to explicitly characterize and compare the longitudinal dynamics of CRP and GDF-15 in patients undergoing elective knee arthroplasty. Characterizing these biomarkers in a controlled acute surgical model provides clinical relevance by mapping systemic acute-phase inflammation against cellular stress pathways, which may offer a baseline reference for evaluating chronic tissue-wasting states.

Methods: This prospective observational study included 47 patients undergoing elective knee arthroplasty. After excluding nine patients with elevated baseline CRP (>10 mg/L), serial measurements of CRP and GDF-15 were analysed daily in 38 patients from pre-operation to postoperative Days 1-3.

Results: CRP rose sharply after surgery, peaking on Day 3 (median: 206.0 mg/L vs. baseline: 3.0 mg/L), representing a maximal increase exceeding 6100%.

GDF-15 levels also increased progressively, peaking on Day 3 (median: 1682.5 pg/mL vs. baseline: 968.8 pg/mL), which represented a statistically significant but more modest rise of 33%.

CRP and GDF-15 were significantly correlated on postoperative day 1 (rs = 0.53, p = 0.001) but not days 2 and 3. Baseline GDF-15, but not CRP, was significantly associated with oral hypoglycaemic agent use and vitamin B12 supplementation.

Compared to values reported in recent randomized trials of ghrelin, anti-GDF-15, and anti-IL-6 therapies, GDF-15 levels in this surgical cohort remained lower, while CRP approached levels observed in such studies. Conclusions: CRP and GDF-15 rise in parallel following surgical injury; however, GDF-15 shows a considerably lower sensitivity to the inflammatory response.

These findings suggest a complementary role of GDF-15 alongside CRP in profiling the perioperative stress response. While its relatively modest acute elevation limits its utility as a primary marker of acute inflammation, this surgical stress model serves as a reference that may help contextualize biomarker profiles in chronic inflammatory or wasting conditions, such as cancer cachexia, rather than serving as a direct tool for cachexia management.