8.5 Biomechanical Loading of Articular Cartilage

  • Forces at joint surface vary from zero to several times body weight
  • “Contact” area varies in a complex manner; typically only several square centimeters
  • Potentially high pressures/stress
  • Think of cartilage behavior with load as biphasic (solid component and water) … wet sponge?

[ ( slide credit: @Jastifer2010Cartilage ) ]

8.5.1 Viscoelasticity

  • Cartilage is viscoelastic
    • Hysteresis
    • Strain rate dependent on time
    • Creep
    • Stress relaxation

[ ( slide credit: @Jastifer2010Cartilage ) ]

8.5.2 Impact of arrangement of collagen on mechanical properties

  • Superficially:
    • Tangential orientation of collagen resists shear as joint surfaces move past each other

@Jastifer2010Cartilage

[ ( slide credit: @Jastifer2010Cartilage ) ]

@Jastifer2010Cartilage

  • Middle:
    • High water content, high Proteoglycan content
    • With early load, water moves to joint space and participates in lubrication
    • With late load, negative charge of Proteoglycan molecules begin to repulse each other and offer resistance to compression
    • Fairly isotropic

[ ( slide credit: @Jastifer2010Cartilage ) ]