ABSTRACT
The mechanical response of articular cartilage is time dependent, and exhibits phenomena such as stress relaxation, creep, and hysteresis. In addition, the material is sensitive to loading rate. The mechanical testing of articular cartilage is either done in vitro, following the resection of the targeted tissue, or in vivo through arthrotomy, or arthroscopy. This chapter focuses on the use of indentation in the evaluation of cartilage properties, and presents an overview of different methodologies used to characterize the properties of articular cartilage as often used in the design of orthopedic animal models. An indentation test is a sensitive way to quantify the viscoelastic response of cartilage by displaying both elastic and time-dependent properties under a compressive load. The properties of articular cartilage were successfully investigated using indentation and friction analysis. The design of an indentation protocol should allow for reproducibility and accuracy, and should take into consideration the time-dependent response of the tissue, its biphasic nature, and its geometry.
