## 3 Biomechanics of Articular Cartilage
### Mechanical Properties of Articular Cartilage
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Typical Value** & **Measurement Method** & **Author** \\ \hline Compressive Young’s modulus (MPa) & 0.24–0.85 & Unconfined compression tests & [PERSON] et al. [51] \\ Hydraulic permeability (m\({}^{4}\)/Ns) & \(10^{-16}\)–\(10^{-15}\) & Confined compression tests, indentation & [PERSON] et al. [172] \\ Poisson’s ratio & 0.06–0.3 & Unconfined compression tests, indentation & [PERSON] et al. [51] \\  & & Unconfined compression tests, indentation & [PERSON] et al. [172] \\ Tensile Young’s modulus (MPa) & 5.0–25.0 & Tensile constant strain rate & [PERSON] et al. [174] \\ Tensile equilibrium modulus (MPa) & 5.0–12.0 & Tensile stress relaxation & [PERSON] et al. [181] \\ Tensile strength (MPa) & 8–25.0 & Tensile constant strain rate & [PERSON] et al. [182] \\ Complex shear modulus (MPa) & 0.2–2.5 & Dynamic shear & [PERSON] et al. [154] \\ Equilibrium shear modulus (MPa) & 0.05–0.4 & Equilibrium shear & [PERSON] et al. [175] \\  & & & [PERSON] et al. [183] \\ Shear loss angle (\({}^{\circ}\)) & 10–15 & Dynamic shear & [PERSON] et al. [176] \\  & & Dynamic shear & [PERSON] et al. [179] \\  & & & [PERSON] et al. [175] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._with the experiment conducted in a closed chamber was demonstrated. [PERSON] [45] described the confined compression test as one of the most repeatable and controllable methods for measuring axial stiffness and flow properties of AC. He indicated its usefulness in analysing SF transport and porosity in the tissue structure. Another measurement method used is the unconfined compression test, which is one of the basic methods of mechanical testing of AC. It consists of axial compression of a cylindrical tissue sample between rigid plates without lateral restriction of fluid flow and deformation [51; 173]. The use of this method enables measurement of the mechanical response of the tissue, taking into account fluid outflow through the lateral surfaces as well as creep and stress relaxation in the axial direction [51; 173]. In the work of [PERSON] et al. [51], this method was used to discuss the mechano-electrochemical phenomena occurring in AC during loading. It was emphasised that this measurement method allows for the assessment of the influence of ion transport and osmotic gradients on the mechanical behaviour of AC. The authors emphasised that the use of the unconfined compression test allows for the study of inhomogeneity and anisotropy depending on the tissue zone. [PERSON] et al. [172] demonstrated the utility of this method in combination with optical analysis to determine the Poisson's ratio in adult bovine AC. The acquired data made it possible to calculate the transverse deformation, providing a basis for mechanical calibration of the imaging techniques. [PERSON] [45] demonstrated that the unconfined compression test is one of the most commonly used tools in tissue biomechanics, which allows for determining axial stiffness and time-dependent response (creep, stress relaxation). He indicated the usefulness of this method for determining the viscoelastic properties of AC. [PERSON] et al. [179] conducted mechanical studies of tissue scaffolds fabricated using the three-dimensional fibre alignment method using the unconfined compression test. This made it possible to determine the influence of the pore geometry and spatial architecture of the scaffolds on stiffness and damping during cyclic loading. Another method of testing the mechanical properties of AC is the indentation test. It consists of applying a controlled load or displacement using an indenter of a specific shape in order to make local contact with the sample surface [51; 178]. This measurement method is used to assess local tissue properties, such as elastic modulus, stiffness, and biphase parameters [51; 178]. [PERSON] et al.