RBP4—a risk factor in lipid metabolism—serves as an early diagnostic and prognostic marker of knee osteoarthritis progression

Knee Osteoarthritis (KOA) represents a prevalent chronic degenerative disorder. Currently, the diagnosis and monitoring of KOA are typically founded on clinical symptoms and imaging examinations when joint damage has already manifested. Consequently, reliable biochemical markers are highly demanded for the early diagnosis of osteoarthritis. This study aimed to investigate whether serum retinol-binding protein 4 (RBP4) levels in patients with primary KOA can serve as a potential biomarker for early joint damage and to analyze their predictive value for the onset and progression of KOA. A case-control study was carried out at the First People’s Hospital of Hefei during the period from December 2024 to February 2025. A total of 160 participants were encompassed in the study (comprising 40 patients diagnosed with early-stage and 40 with late-stage KOA, and 80 age-matched healthy controls). Serum levels of RBP4, C-reactive protein (CRP), Cartilage oligomeric matrix protein (COMP), and matrix metalloproteinase-3 (MMP-3) were quantified using sandwich enzyme-linked immunosorbent assay (ELISA). Erythrocyte sedimentation rate (ESR) was determined via the Infrared ESR Analyzer. Finally, an early diagnostic model for KOA was developed and evaluated for its predictive performance. RBP4 levels were significantly elevated in patients with KOA, with late-stage disease exhibiting markedly higher concentrations compared to early-stage counterparts. Serum RBP4 exhibited a positive correlation with symptom duration, age, Body Mass Index (BMI), visual analogue pain scores (VAS), Kellgren and Lawrence (KL) grade, MRI grade, CRP, COMP, and MMP-3, but negatively correlated with hospital for special surgery knee score (HSS). The area under the Receiver Operating Characteristic (ROC) curve (AUC) for the diagnosis of RBP4 is 0.878, and the AUC for differentiating controls and early-stage KOA is 0.832. Serum RBP4 is a lipid metabolism–related biomarker that correlates with KOA severity and exhibits strong early-stage diagnostic performance.