Association of High-Sensitivity C-Reactive Protein and Interleukin-6 with Low Back Pain Intensity in Patients with Knee Osteoarthritis

Abstract

Knee osteoarthritis is a prevalent degenerative joint disease among older adults and often occurs alongside low back pain (LBP). High-sensitivity C-reactive protein (hs-CRP) and interleukin-6 (IL-6) have been linked to the severity of osteoarthritis; however, their relationship with the intensity of LBP remains inadequately defined. This study aims to analyse the association between hs-CRP and IL-6 levels and LBP intensity in patients diagnosed with knee osteoarthritis. An analytic observational cross-sectional study was conducted involving 84 patients with knee osteoarthritis (Kellgren-Lawrence grades II-IV) at a regional hospital in South Kalimantan, Indonesia, from November 2025 to February 2026. Serum levels of hs-CRP and IL-6 were quantified using enzyme-linked immunosorbent assay, while LBP intensity was measured using the Visual Analogue Scale (VAS). Associations between variables were examined using Pearson's or Spearman's correlation, as appropriate, along with multiple linear regression analysis.  The participants had a mean age of 61.93 ± 11.08 years, comprising 42 men and 42 women. The median hs-CRP level was 1.75 mg/L (interquartile range 1.10-2.40), and the mean IL-6 level was 2.57 ± 1.93 pg/mL. The average VAS score recorded was 4.88 ± 1.35. A strong correlation was found between hs-CRP and the VAS score (Pearson r=0.813, p<0.001), whereas IL-6 demonstrated a weak, non-significant correlation (Spearman r=0.173, p=0.166). Together, hs-CRP and IL-6 accounted for 70.5% of the variance in VAS scores (R²=0.705, p<0.001) in the multiple linear regression model, with hs-CRP identified as the predominant predictor. The results suggest a strong association between hs-CRP and LBP intensity in individuals with knee osteoarthritis, while IL-6 exhibited a consistent yet non-significant relationship. These findings indicate that systemic inflammation may serve as a quantifiable contributor to LBP and point out the potential of hs-CRP as a clinical indicator for assessing pain severity.