New directions for the characterisation of cartilage health in vivo

This paper outlines the motivation and preliminary investigations into the possibility of a new method of characterising cartilage health in vivo. Current in vivo indentation techniques, which rely on stiffness measurements alone, are unable to adequately distinguish between healthy and degraded tissue. By considering the tangential strain in the articular surface during an indentation test, it is hypothesised that a simple and more sensitive indicator of cartilage integrity may be possible. The present study investigates the effects of low levels of degradation on the tangential surface strain under the indenter. Preliminary results suggest that this technique is highly sensitive, and can discriminate between degeneration and the natural variations across the joint. From these investigations we propose that the relationship between indentation and the surrounding strain field might be able to distinguish between healthy soft tissue and degraded tissue in vivo, important information not available from the current techniques. This study forms the basis of a series of further experimental and modelling investigations to develop these ideas with the goal of creating a more effective diagnostic method for the surgeon.