Nanoscale study of cartilage surfaces using atomic force microscopy.

Articulating cartilage wear plays an important role in cartilage degeneration and osteoarthritis (OA) progression. This study investigated the changes of mechanical properties and surface roughness of sheep cartilages with wear progression at a nanometre scale. Young sheep's rear legs were subjected to a series of wear tests to generate worn cartilage samples to simulate the OA progression. Atomic force microscopy (AFM) was used to determine the effective indentation modulus and to measure the surface morphology of moist cartilage surfaces. The study has found that the mean effective indentation modulus values of worn cartilages were lower than that of healthy cartilage as the control sample. A medium-to-strong correlation between the effective indentation modulus values and the OA grades has been found. The relation between surface topography and effective indentation modulus values of the cartilage surfaces with OA progression was weakly correlated. The method established in this study can be implemented to investigate the effective indentation modulus values of clinical osteoarthritic cartilages and to assist in the understanding and assessment of OA.