Serum COMP and Vitamin D as a Biomarker for Articular Cartilage Degeneration in Knee Osteoarthritis: Correlation with USG and MRI Findings.

Background/Objectives: Osteoarthritis (OA) remains a global health problem, as it can cause permanent joint damage, leading to irreversible disability. Therefore, there is a need for accessible and non-invasive alternative examinations, such as USG, serum COMP, and 25-hydroxyvitamin D [25(OH)D] assessment. This study aims to analyze the correlation between serum COMP and 25(OH)D levels and the degree of articular cartilage degradation in patients with knee OA, based on findings from USG and MRI examinations. Methods: A cross-sectional analytical study was conducted at Mohammad Hoesin Hospital, Palembang, from December 2024 to August 2025. 31 patients diagnosed with knee OA based on the 1990 American College of Rheumatology (ACR) classification criteria were enrolled. Serum COMP and 25(OH)D levels were measured. All patients underwent standardized USG and MRI examinations of the knee. Spearman's rank correlation coefficient was used for statistical analysis. Results: The majority of the study subjects were female, comprising 23 (74.2%). The mean age was 63.90 ± 7.77 years with a body mass index of 25.46 ± 5.51 kg/m2. Most subjects were engaged in heavy physical activity 17 (54.8%). Laboratory examination showed serum COMP levels with a median of 869 ng/mL and a range of 136-3302 ng/mL. Meanwhile, the 25(OH)D level demonstrated a mean value of 24.84 ± 7.33 ng/mL. The analysis revealed a strong and statistically significant positive correlation between serum COMP levels and the degree of articular cartilage degradation in knee OA. This correlation was observed in both USG (r = 0.61; p < 0.001) and MRI assessments (r = 0.72; p < 0.001). In contrast, serum 25(OH)D levels showed no significant correlation with cartilage degradation. The correlation coefficient between 25(OH)D levels and USG-assessed cartilage degradation was r = -0.12 (p = 0.51), and for MRI assessment, it was r = 0.17 (p = 0.92). Conclusions: A strong and significant positive correlation exists between serum COMP levels and the degree of articular cartilage degradation based on USG (r = 0.61; p < 0.001) and MRI (r = 0.72; p < 0.001). In contrast, serum 25(OH)D levels showed no significant correlation with cartilage degradation, implying that 25(OH)D may not directly reflect the extent of structural cartilage damage in knee osteoarthritis. This finding proves that an increase in serum COMP levels is associated with an increase in the degree of articular cartilage degradation in knee OA as measured by both USG and MRI.