Mechanical Behavior of Articular Cartilage Under Impact Loading

Articular cartilage is a specialised load‐bearing tissue that covers the ends of bones in synovial joints, providing low‐friction surfaces and distributing mechanical loads. Under impact loading, its response is governed by a combination of fluid pressurisation within the porous extracellular matrix and intrinsic viscoelastic properties of the solid matrix. At high strain rates, interstitial fluid bears a greater proportion of the load, resulting in increased apparent stiffness and reduced deformation. Conversely, at lower rates, fluid can exude from the matrix, leading to greater energy dissipation and viscoelastic damping. The cartilage structure is zonal, with a superficial tangential layer rich in collagen fibrils resisting shear, a middle zone providing compressive resilience, and a deep zone anchoring the tissue to subchondral bone. Impact loads may induce microcracks in collagen or propagate fissures at the cartilage–bone interface, initiating degeneration. The biphasic theory frames this behaviour by treating cartilage as a two‐phase material—solid matrix and fluid—allowing models to predict force‐displacement responses under rapid loading. Understanding impact mechanics is crucial for elucidating injury mechanisms in sports, designing protective equipment, and guiding therapeutic interventions aimed at preserving cartilage integrity after acute trauma.

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Mechanical Behavior of Articular Cartilage Under Impact Loading publication trend

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Technical terms

Articular cartilage: A specialised connective tissue lining joint surfaces, composed of chondrocytes embedded in an extracellular matrix of collagen, proteoglycans and interstitial fluid.

Viscoelasticity: The property of a material to exhibit both elastic (energy‐storing) and viscous (energy‐dissipating) responses under deformation.

Storage modulus (E′): A measure of the elastic, energy‐storing component of a viscoelastic material under oscillatory loading.

Loss modulus (E″): A measure of the viscous, energy‐dissipating component of a viscoelastic material under oscillatory loading.

Strain rate: The speed at which deformation is applied to a material, typically expressed as change in strain per unit time, influencing fluid pressurisation and matrix response.

Biphasic theory: A modelling framework treating cartilage as two interpenetrating phases—solid matrix and interstitial fluid—to predict time‐dependent mechanical behaviour under load.

References

1. The Biomechanics of Cartilage—An Overview. Life (2021).
2. Viscoelasticity of articular cartilage: Analysing the effect of induced stress and the restraint of bone in a dynamic environment. Journal of the Mechanical Behavior of Biomedical Materials (2017).
3. Viscoelastic properties of human and bovine articular cartilage: a comparison of frequency-dependent trends. BMC Musculoskeletal Disorders (2016).
4. Impact testing to determine the mechanical properties of articular cartilage in isolation and on bone. Journal of Materials Science: Materials in Medicine (2007).