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 concentration of procollagen IIC-peptide in joint fluid significantly correlates with mechanical risk factors of knee osteoarthritis (OA), such as obesity (body 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, Ahlbäk stage I. The relations between procollagen IIC-peptide and body mass index and lateral femorotibial angle were examined using simple regression analysis and multiple regression analysis.

RESULTS

Significant positive correlations were found between procollagen IIC-propeptide concentrations and body mass index (r=0.479, p<0.0001), and between procollagen IIC-propeptide concentrations and lateral femorotibial angle (r=0.375, p=0.0021). Significant correlations were also found by multiple regression analysis. The multiple correlation coefficient of body mass index and femorotibial lateral angle to the procollagen IIC-propeptide concentrations was 0.547 (p<0.0001).

CONCLUSIONS

The findings suggest that synthesis of type II collagen by chondrocytes is enhanced by abnormal mechanical stress, in this case obesity and varus alignment. It is concluded that procollagen IIC-propeptide concentrations in joint fluid are a useful marker of early OA.