Consequences of Long-Term Cyclic Indentation on Initially Intact Cartilage

It has long been suggested that articular cartilage is susceptible to damage by repetitive mechanical loading (1–4); however, the exact mechanisms via which the damage is induced is not yet well-understood. As a step towards deeper understanding of damage, this work sought to address two main goals: (i) to investigate the consequences of subjecting initially intact cartilage to repeated long-term small-amplitude indentation loading that does not induce any observable damage over a short term; and (ii) to establish a 1-D nonlinear rheological model to capture the indentation response of the tissue in its “undamaged” and “damaged” states. Our objective is to use a simple model to provide a framework to interpret the changes in the macroscopic mechanical response in terms of alterations in its constituents properties.