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Biomechanics of Cartilage
Sunil
MPT – 1 SEM
Fibrocartilage
White Fibrocartilage contains bundles of white fibrous tissue
which give it great tensile strength with som...
• All three structures are composed of water, collagen,
and proteoglycans (PGs)
• Nucleus Pulposus: 70% to 90% water, depe...
ELASTIC CARTILAGE
• Yellow Fibrocartilage contains bundles of elastic fibres with
little or no white fibrous tissue.
• It ...
HYALINE CARTILAGE
• Hyaline cartilage forms the temporary skeleton of the fetus
from which bones develop. Its remnants can...
Biomechanics of Articular Cartilage
Microstructure of cartilage
• The cells of cartilage are chondroblasts and chondrocytes.
• Chondrocytcs manufacture, secre...
WATER
• The fluid component of articular cartilage is also essential
to the health of this avascular tissue because it per...
COLLAGEN
• Collagens consist of 3 polypeptide chains
that form a triple helix
• They can be divided into fibrillar
collage...
• More than 20 different types collagen identified so far, the
functions of all of these types have not been determined.
•...
• Collagens—
structure,
function, and
biosynthesis
• K. Gelsea, E.
Po¨schlb, T.
Aignera,*
PROTEOGLYCAN
.
A large protein-polysaccharide molecule composed of a protein core
to which one or more glycosaminoglycans ...
STRUCTURAL AND PHYSICAL INTERACTION
AMONG CARTILAGE COMPONENTS
• The closely spaced sulfate and carboxyl
charge dissociate...
• Collagen fibrils and PGs, each being capable of
forming structural networks of significant
strength.
• These structural ...
MATERIAL PROPERTIES
• A confined compression test commonly used methods for
determining material properties of cartilage.
...
• In relaxation mode : a constant displacement
is applied to the tissue, and the force needed
to maintain the displacement...
Aggregate modulus and permeability
• The aggregate modulus is a measure of the stiffness of the
tissue at equilibrium when...
Stress and strain
Young’s modulus
• If the fluid flowed easily out of the tissue, then the solid
matrix would bear the full contact stress, and under this
i...
• Compression is minimized because of the high proteoglycan
concentration, and this serves to protect the chondrocytes fro...
MECHANICAL FAILURE OF CARTILAGE
• A characteristic feature of osteoarthrosis is cracking,
fibrillation, and wear of cartil...
• Repeated compressive loads applied to the
cartilage surface in situ also cause a decrease
in tensile strength, if a suff...
The effects of repeated tensile loading on the tensile strength of cartilage.
As the tensile loading stress increases, few...
JOINT LUBRICATION
Lubrication of articulating cartilage surfaces by SF is mediated by
several lubricant macromolecules syn...
• From an engineering perspective, there are two fundamental
types of lubrication.
• One is boundary lubrication, which in...
Hypotheses on the Biomechanics
of Cartilage Degeneration
ROLE OF BIOMECHANICAL FACTORS
• Magnitude of the imposed stresses...
IMPLICATIONS ON CHONDROCYTE
FUNCTION
• In healthy articular cartilage, loads from
normal joint function motion result in t...
MODELS OF OSTEOARTHROSIS
• Animal models are used to provide a controlled environment
for studying the progression of oste...
Effects of aging on articular cartilage
Changes in cells
• Reduced cell density,
• Reduced responsiveness to growth factor...
• There is evidence showing that HMGB2, a high-mobility group
box (HMGB) protein that may be important for chondrocyte
sur...
• During aging, chondrocytes exhibit reduced responsiveness to
growth factors, such as insulin-like growth factor-1 (IGF-1...
ECM
• Advanced glycation end-product (AGEs) increase collagen
cross-linking, which enhances tissue stiffness, making
carti...
The effects of immobilization on the characteristics of
articular cartilage
• With immobilization, there is connective tis...
• Mechanical loading of AC stimulates the metabolism of
chondrocytes and induces the biosynthesis of molecules to
preserve...
The effects of exercise on human
articular cartilage
• Enhance synovial movement for cartilage nutrition
• Dynamic (cyclic...
Resistive Exercise for Arthritic Cartilage Health (REACH): A randomized double-blind, sham-exercise controlled
trial
Angel...
Special thanks to Dr. Saurabh Sharma sir
for his guidance and assistance
Cartilage  by sunil
Cartilage  by sunil
Cartilage  by sunil
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Cartilage by sunil

  1. 1. Biomechanics of Cartilage Sunil MPT – 1 SEM
  2. 2. Fibrocartilage White Fibrocartilage contains bundles of white fibrous tissue which give it great tensile strength with some elasticity, so that it is able to resist considerable pressure. • Intervertebral discs • Menisci of knee joint • Labrum surrounding and deepening the glenoid fossa of shoulder joint • Articular discs of radiocarpal, strenoclavicular, AC and temporomandibular joint. • White fibrocartilage may calcify and ossify
  3. 3. • All three structures are composed of water, collagen, and proteoglycans (PGs) • Nucleus Pulposus: 70% to 90% water, depending on age and time of day. Collagen fibers contribute 15% to 20% of the dry weight and 65% is of PGs. • Anulus Fibrosus: Collagen fibers make up 50% to 60% of the dry weight. And 10% elastin. • Vertebral End Plates: 0.6 to 1mm thick, both hyaline cartilage and fibrocartilage present. But with increasing age, no hyaline cartilage remaining
  4. 4. ELASTIC CARTILAGE • Yellow Fibrocartilage contains bundles of elastic fibres with little or no white fibrous tissue. • It does calcify or ossify and is not found in musculoskeletal system. • Elastic cartilage is found in the epiglottis, larynx and the pinnae.
  5. 5. HYALINE CARTILAGE • Hyaline cartilage forms the temporary skeleton of the fetus from which bones develop. Its remnants can be seen as the articular cartilages of synovial joint, the epiphyseal growth plates between parts of an ossifying bone during growth, and the costal cartilages of the ribs. • It has a white, lustrous and smooth appearance. • It provide a smooth surface permitting free movement to occur and resist the compressive forces encountered across the joint under loading. • With increasing age, hyaline cartilage tends to become calcified and sometimes ossified.
  6. 6. Biomechanics of Articular Cartilage
  7. 7. Microstructure of cartilage • The cells of cartilage are chondroblasts and chondrocytes. • Chondrocytcs manufacture, secrete, organize and maintain the organic component of the extracellular matrix. • The organic matrix, is composed of dense network of fine collagen fibrils.
  8. 8. WATER • The fluid component of articular cartilage is also essential to the health of this avascular tissue because it permits gas, nutrient, and waste product movement back and forth between chondrocytes and the surrounding nutrient-rich synovial fluid • Most of the water thus occupies the inter space of the ECM and is free to move when a load or pressure gradient or other electrochemical motive forces are applied to the tissue. 60 to 85% is water
  9. 9. COLLAGEN • Collagens consist of 3 polypeptide chains that form a triple helix • They can be divided into fibrillar collagens(types I, II, III, V and XI), which form the framework of the tissue 60 to 70% of the dry weight
  10. 10. • More than 20 different types collagen identified so far, the functions of all of these types have not been determined. • The fibril-forming collagens (types I, II, III, V, and XI) are the most common. • Type I collagen, comprising 90% of the total collagen in the body, is found in almost all connective tissue, including tendons, ligaments, menisci, fibrocartilage, joint capsules, bones, labra, and skin. • Type II collagen is found mainly in hyaline articular cartilage and in the nucleus pulposus in the center of the intervertebral disks. • Type III collagen is found in the skin.
  11. 11. • Collagens— structure, function, and biosynthesis • K. Gelsea, E. Po¨schlb, T. Aignera,*
  12. 12. PROTEOGLYCAN . A large protein-polysaccharide molecule composed of a protein core to which one or more glycosaminoglycans (GAGs) are attached. 30% of the dry weight
  13. 13. STRUCTURAL AND PHYSICAL INTERACTION AMONG CARTILAGE COMPONENTS • The closely spaced sulfate and carboxyl charge dissociate in solution at physiological pH leaving a high concentration of fixed negative charges that create strong intramolecular and intermolecular repulsive forces. When cartilage is compressed, the negatively charged sites on aggrecan are pushed closer together, which increases their mutual repulsive force and adds to the compressive stiffness of the cartilage.
  14. 14. • Collagen fibrils and PGs, each being capable of forming structural networks of significant strength. • These structural components support the internal mechanical stresses that result from loads being applied to the articular cartilage.
  15. 15. MATERIAL PROPERTIES • A confined compression test commonly used methods for determining material properties of cartilage. • A “creep” mode : a constant load is applied to the cartilage through a porous plate, and the displacement of the tissue is measured as a function of time
  16. 16. • In relaxation mode : a constant displacement is applied to the tissue, and the force needed to maintain the displacement is measured.
  17. 17. Aggregate modulus and permeability • The aggregate modulus is a measure of the stiffness of the tissue at equilibrium when all fluid flow has ceased. • The higher the aggregate modulus, the less the tissue deforms under a given load. • The average fluid velocity is proportional to the pressure gradient • The constant of proportionality is called the permeability. • The aggregate modulus of cartilage is typically in the range of 0.5 to 0.9 Mpa. • The Young’s modulus of cartilage is in the range of 0.45 to 0.80 MPa.
  18. 18. Stress and strain
  19. 19. Young’s modulus
  20. 20. • If the fluid flowed easily out of the tissue, then the solid matrix would bear the full contact stress, and under this increased stress, it might be more prone to failure. • The lower modulus and increased permeability of osteoarthrotic cartilage result in greater and more-rapid deformation of the tissue than normal.
  21. 21. • Compression is minimized because of the high proteoglycan concentration, and this serves to protect the chondrocytes from adverse forces. • This protection breaks down when the joint is subjected to excessive loads or overuse, as the chondrocytes release proteolytic enzymes which damage the proteoglycan and collagen so causing tissue degeneration In general, dynamic (cyclic) loading is beneficial to matrix synthesis, whereas static loading is detrimental • Abnormally high compression loads may lead to articular cartilage changes and deterioration
  22. 22. MECHANICAL FAILURE OF CARTILAGE • A characteristic feature of osteoarthrosis is cracking, fibrillation, and wear of cartilage. Studies of the tensile failure of cartilage are primarily concerned with variations in properties among joints, the effects of repeated load, and age.
  23. 23. • Repeated compressive loads applied to the cartilage surface in situ also cause a decrease in tensile strength, if a sufficient number of load cycles are applied. • Repeated tensile loading (fatigue) lowers the tensile strength of cartilage as it does in many other materials. As the peak tensile stress increases, the number of cycles to failure decreases
  24. 24. The effects of repeated tensile loading on the tensile strength of cartilage. As the tensile loading stress increases, fewer cycles of loading are needed to cause failure. Age is also an important factor.Cartilage from older individuals fails at a lower stress than that from younger people.
  25. 25. JOINT LUBRICATION Lubrication of articulating cartilage surfaces by SF is mediated by several lubricant macromolecules synthesized and secreted by synovial cell populations and found in SF. • Normal synovial joints operate with a relatively low coefficient of friction, about 0.001 • Identifying the mechanisms responsible for the low friction in synovial joints has been an area of ongoing research for decades
  26. 26. • From an engineering perspective, there are two fundamental types of lubrication. • One is boundary lubrication, which involve as a single monolayer of lubricant molecules adsorbed on each bearing surface. • The other is fluid-film lubrication, in which a thin fluid-film provides greater surface-to-surface separation • Combination of boundary lubrication (at low loads) and fluid film lubrication (at high loads) is responsible for the low friction in synovial joint
  27. 27. Hypotheses on the Biomechanics of Cartilage Degeneration ROLE OF BIOMECHANICAL FACTORS • Magnitude of the imposed stresses. • The total number of sustained stress peaks. • The changes in the intrinsic molecular and microscopic structure of the collagen-PG matrix. • The changes in the intrinsic mechanical property of the tissue. • Loosening of the collagen network, that allow abnormal PG expansion and thus tissue swelling.
  28. 28. IMPLICATIONS ON CHONDROCYTE FUNCTION • In healthy articular cartilage, loads from normal joint function motion result in the generation of mechano-ectrochemical stimuli that promote normal cartilage maintenance. • trauma or disease leads to abnormal mechano-ectrochemical stimuli,
  29. 29. MODELS OF OSTEOARTHROSIS • Animal models are used to provide a controlled environment for studying the progression of osteoarthrosis. • various mechanical alterations of a joint lead to the development of osteoarthrosis. • Surgical alterations may be small, suggesting that altered forces are primarily responsible for the developing osteoarthrosis. • Impulsively applied loads were found to produce osteoarthrosis, while higher loads applied at a lower rate do not
  30. 30. Effects of aging on articular cartilage Changes in cells • Reduced cell density, • Reduced responsiveness to growth factors. Changes in extracellular matrix • Increase Advanced glycation end-product (AGEs) • The cumulative effect of mechanical load over the years may cause “wear and tear” Effects of aging on articular cartilage homeostasis by Martin Lotz a,, Richard F. Loeser b
  31. 31. • There is evidence showing that HMGB2, a high-mobility group box (HMGB) protein that may be important for chondrocyte survival, Decline in HMGB2 levels was associated with increased chondrocyte death. • Levels of Reactive oxygen species (ROS) are increased in cartilage during aging, and chondrocytes from older adults are more susceptible to ROS mediated cell death. • Mechanical injury to cartilage, such as articular cartilage crushing, shearing force injury, would result in elevated ROS generation in mitochondria and promotes chondrocyte death. • Evidence has been shown that mitochondrial DNA damage in OA is promoted by inflammatory cytokines such as IL-1𝛽 and tumor necrosis factor- 𝛼 (TNF-𝛼 ) and contributes to chondrocyte death The Age-Related Changes in Cartilage and Osteoarthritis YongPing Li,1 XiaoChun Wei,1 JingMing Zhou,2 and Lei Wei1,2
  32. 32. • During aging, chondrocytes exhibit reduced responsiveness to growth factors, such as insulin-like growth factor-1 (IGF-1) , osteogenic protein-1 (OP-1) or bone morphogenic protein-7, and transforming growth factor-𝛽 (TGF-𝛽) • For example, TGF-𝛽 stimulates proteoglycan synthesis in young animals, but this ability is impaired in old mice • In chondrocytes, AGEs can increase the production of inflammatory cytokine (TNF-𝛼), inflammatory mediators prostaglandin E2, and nitric oxide. It can also suppress the production of type II collagen.
  33. 33. ECM • Advanced glycation end-product (AGEs) increase collagen cross-linking, which enhances tissue stiffness, making cartilage more brittle and susceptible to mechanical failure. • AGEs are produced through a non enzymatic reaction between reducing sugars and free amino groups of proteins • Age-related changes in size, structure, and sulfation of aggrecan affect cartilage resiliency and hydration. Safranin O stained sections of human femoral condyles. Images show young normal (left, age 40), old normal (center, age 76) and OA donors (right, age 88).
  34. 34. The effects of immobilization on the characteristics of articular cartilage • With immobilization, there is connective tissue weakening, articular cartilage degeneration so it not able to withstand large compressive forces. • Rapid destruction of articular cartilage occurs with immobilization because the cartilage is not being bathed by moving synovial fluid and is thus deprived of its nutritional supply. • Vanwanseele et al. showed that cartilage thickness decreases after spinal cord injury . • Knee joint immobilization leads to reduced GAG content, especially from the SZ, with unchanged collagen content. J. Funct. Morphol. Kinesiol. 2016, ; doi:10.3390/jfmk1020154
  35. 35. • Mechanical loading of AC stimulates the metabolism of chondrocytes and induces the biosynthesis of molecules to preserve the integrity of the tissue. • Mechanoreceptors initiates intracellular signaling cascades, leading to the tissue remodeling process.
  36. 36. The effects of exercise on human articular cartilage • Enhance synovial movement for cartilage nutrition • Dynamic (cyclic) loading is beneficial to matrix synthesis.
  37. 37. Resistive Exercise for Arthritic Cartilage Health (REACH): A randomized double-blind, sham-exercise controlled trial Angela K Lange*1, Benedicte Vanwanseele1, Nasim Foroughi1, Michael K Baker1, Ronald Shnier2, Richard M Smith1 and
  38. 38. Special thanks to Dr. Saurabh Sharma sir for his guidance and assistance
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