1. Cortical Bone Trabecular Bone Meniscus Articular Cartilage
Hyaline Cartilage
articular cartilage
larynx
rib and costal cartilage
nasal septum
Elastic Cartilage
epiglottis
Fibrocartilage
Intervertebral disk
meniscus
Cortical Bone
Trabecular Bone
Meniscus
Articular
Cartilage
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Tissues are classified by their biochemical composition, molecular microstructure, biomechanical properties and function.

3. Support large loads Lubrication AC/Meniscus Functions: gymnastics
Walking
Lubrication
Interested in these structures because
when they “breakdown” we get
osteoarthritis

4. Articular Cartilage Important to understand
Mechanical properties of normal cartilage
Manner by which biochemical and structural factors contribute to the material properties of cartilage
Manner by which changes in tissue composition affect the mechanical properties of cartilage

5. Diarthrodial joint Fibrous capsule
Inside lined with synovium which secretes synovial fluid

6. Microstructure (Solid and Fluid Phase)
Interstitial water
Articular cartilage 68-85%, meniscus 60-70%

7. Interstitial Water Constant with age Increases with OA or degeneration
Amount of water is dependent on

8. Interstitial water Ions-
As tissue is compressed-Frictional drag force on walls of the pores of the solid matrix due to interstitial fluid flow through the pores of collagen-PG matrix

9. Microstructure (Solid and Fluid Phase)
Collagen
Proteoglycans
Cells
No blood or nerves in cartilage

10. Collagen: made up of molecules (tropocollagen--1
Collagen: made up of molecules (tropocollagen--1.4 nm) that polymerize to form fibrils
Type II (AC), forms bundles, with diam.=2 to 10 microns
Type I (meniscus), forms fibrils, with diam. = nm

11. Collagen Orientation

12. Collagen Orientation

13. Proteoglycan: protein with bound side chains (glycosaminoglycans)

14. Proteoglycans Negative charge attracts +ions (K and Na)
Swelling pressure
PG want to be 5-10 times larger, but not enough room in cartilage

15. Cells: Chondrocytes

17. Material Properties Steel is linear elastic (E,)
Soft tissues ARE NOT!!
Water movement (forces depend on rate-damping)
STEEL

18. Material Properties
Viscoelastic behavior are dominated by frictional drag of interstitial fluid flow through the porous collagen-proteoglycan solid matrix, thus causing viscous dissipation

19. Material Properties-Anisotropy/Inhomogeneous
Transversely Isotropic
Inhomogeneous

20. Constitutive Equation:
Linear Elastic Materials (Steel)
Hookes’ Law:  = E
Viscoelastic materials (AC/meniscus)
Biphasic Theory (2 phase)
Triphasic Theory (3 phase)

21. Tension Equilibrium Tensile Modulus (1-30 MPa) Type of tissue
Age of animal
Type of joint
Sample location
Depth of sample (surface = 10MPa, Middle =4.5MPa)
Relative orientation
Biochemical comp/ molecular structure
State of degeneration (Normal =10MPa, OA=1.4MPa)
Deform.
time
Force
Tensile Stress Relaxation Test

22. Tension

23. Compression Compressive Aggregate Modulus (HA)(0.4-1.5 MPa) Force
Deform
time
time
Confined Compression Creep Test

24. Compression
HA varies inversely with water content *OA patients have increased water
HA varies directly with PG content
Not dependent on collagen content

25. Shear

26. Shear

27. Methods of Failure-Cartilage
Fracture –
Fracture with Bone
Wear
Degeneration
Blunt Trauma (intense compression and shear forces)
Bone
Bone

28. Methods of Failure - Meniscus
Degeneration
Tearing