Procollagen IIC-peptide as a marker for assessing mechanical risk factors of knee osteoarthritis: effect of obesity and varus alignment

Objective-To ascertain by cross sectional examination whether the concentra tion of procollagen IIC-peptide in joint fluid significantly correlates wit h mechanical risk factors of knee osteoarthritis (OA), such as obesity (bod y mass index) and varus alignment (lateral femorotibial angle). Methods-The concentrations of procollagen IIC-propeptide in synovial fluid were measured by a sandwich enzyme immunoassay of 65 patients with the same radiological stage of primary knee OA-that is, Ahlbak stage I. The relatio ns between procollagen IIC-peptide and body mass index and lateral femoroti bial angle were examined using simple regression analysis and multiple regr ession analysis. Results-Significant positive correlations were found between procollagen II C-propeptide concentrations and body mass index (r=0.479, p<0.0001), and be tween procollagen IIC-propeptide concentrations and lateral femorotibial an gle (r=0.375, p=0.0021). Significant correlations were also found by multip le regression analysis. The multiple correlation coefficient of body mass i ndex and femorotibial lateral angle to the procollagen IIC-propeptide conce ntrations was 0.547 (p<0.0001). Conclusions-The findings suggest that synthesis of type II collagen by chon drocytes is enhanced by abnormal mechanical stress, in this case obesity an d varus alignment. Pt is concluded that procollagen IIC-propeptide concentr ations in joint fluid are a useful marker of early OA.