Joint Tissues Flashcards
What does tissue function depend on?
cell structure and function - determined by extracellular components
What is the study of how different materials and structures are able to provide support in response to changing forces?
mechanical behavior of tissue (deals with relationship between stress and strain)
What is the resistance of a material to deformation?
stress
What is stress “formula”?
force/unit area
What is the deformation that occurs in a material in response to the application of an external load quantified as a percentage of change?
strain
What are isotropic materials?
homogenous, exhibit uniform properties when loaded in different directions
What are anisotropic materials?
heterogenous, exhibit non-uniform properties when loaded in different directions
What is the application of a force, moment, or combination of them to a material?
load
What force is equal and opposite loads applied away from the surface of a structure?
tension
What does tension result in?
lengthening and narrowing of structure and causes tensile stresses to occur
What force is equal and opposite loads applied toward the surface of a structure?
compression
What does compression result in?
shortening and widening and causes compression stress
What force is opposing loads applied parallel to the surface of a structure?
shear
What does shear result in?
internal angular deformation and leads to shear stress
What force is opposing loads are applied to the surface of a structure resulting in twisting about an internal axis?
torsion
What does torsion result in?
compression and tension and shear stresses
What is bending?
three or more loads applied to a structure causing it to bend about an axis external to itself
What is combined stress?
combination or two or more loading modes applied to a structure at the same time
What is deformation?
change occurring in some dimension of the material in response to an applied load
What region of the load-deformation curve signifies the removal of slack within a structure as tensile load is applied?
toe region
What region of the load-deformation curve signifies the range in which stress is directly proportional to strain but all the deformation will return to normal after load removal?
elastic range
What part of the load-deformation curve signifies the end of the elastic region when load goes to permanent deformation?
elastic limit/yield point
What region of the load-deformation curve is the range in which deformation occurs at a rate disproportional to stress and permanent structure remains intact?
plastic region
What is the point of the load-deformation curve in which continued load and max load is reached and deformation continues until failure?
ultimate failure point
What region of the load-deformation curve does the removal of crimp occur?
toe region
What effect does increasing fiber quantity have on response to load?
increases strength, stiffness, and elongation to failure is the same - can resist more load
What effect does increasing fiber length have on response to load?
increases elongation to failure, strength remains, stiffness decreases
What is Young’s modulus?
linear portion of the curve in the elastic region measuring the stiffness/resistance to the external loads (inverse = compliance)
If the slope is steep and modulus is high, material exhibits _ stiffness and _ compliance.
high, low
Name an example of high stiffness, low compliance in the body.
cortical bone
If the slope is gradudal and modulus is low, material exhibits _ stiffness, _ compliance.
low, high
Name an example of low stiffness, high compliance in the body.
adipose tissue
What is the stress-strain curve?
load-deformation curve in which load is expressed as load per unit area and strain is expressed as deformation per unit of length or percentage of deformation
The following characteristics explains what region of the stress-strain curve for collagenous materials?
very little force to deform tissue in straightening crimp,
tests for ligament integrity when performed on non-injured ligaments, slack taken up in tendon by its attached muscle before force is transmitted to bone
toe region
The following characteristics explains what region of the stress-strain curve for collagenous materials?
Collagen fibrils are being stretched and are resisting applied force
reflects the type of collagen, fibril size, and cross-linking among collagen molecules
when the load is removed, structure will return to its pre-stressed dimensions (will take time)
includes stress and strains that occur within normal activities
typically extends to about 4% strain
elastic region
The following characteristics explains what region of the stress-strain curve for collagenous materials?
failure of collagen fibers begins,
structure no longer capable of returning to OG length after force is removed
recovery requires considerable time - healing
plastic region
What are clinical examples of plastic region injuries?
Grade I and II ligament sprains/tendon strains
The following characteristics explains what region of the stress-strain curve for collagenous materials?
remaining collagen fibrils experience increased stress and rapidly rupture sequentially
creates overt failure of the tissue
beyond ultimate failure point
Failure through the middle of a ligament or tendon is called what?
rupture
Failure at bony attachment of a ligament or tendon is called what?
avulsion
Failure within bony tissue is called what?
fracture
Deformation prior to failure depends on what things?
tissue type and size
What is the ability of a material to resist flow and dampen shear forces?
viscosity
What is the ability of a material to return to its OG shape following deformation?
elasticity
What are the time-dependent properties?
creep, hysteresis, stress-relaxation
What is creep?
progressive strain or deformation of a structure under the influence of a constant stress/load
True/False: For creep, Force remains constant while length changes.
true
What might creep be applied to in the clinical setting?
stretching a shortened tissue - constant force applies and tissue gradually elongates
What is stress-relaxation?
decrease in stress within a structure in the presence of a constant strain
What does stress-relaxation look like in clinical setting?
therapist may perceived this as a reduced resistance to stretch ex: prolonged static splinting
What is hysteresis?
lag of an effect when forces acting upon a material are changes (energy lost as heaT)
What are the determinant properties of fibrous connective tissue?
size and density of the structure, mechanical properties and proportion of collagen and elastin, orientation of fibers in the tissue
Which of the following is not a mechanical property of fibrous connective tissue?
a. high tensile strength
b. anisotropic
c. stiffness changes with changes in speed of loading
d. have significant viscoelastic characteristics
c - stiffness does not change
Fails at strains occurs as low as 9% for stuctures with _ elastin fiber content.
little/no
Fails at strains occur up to 70% for structures with _ elastin content.
high
True/False: Ultimate load and strain increase with increasing speed of loading.
true
True/False: Aging results in general loss of collagen content, but increase in collagen cross-linking.
true
True/False: The use of NSAIDs can cause a decrease in the tensile strength of CTs due to a decrease in collagen content and in the proportion of non-soluble collagen.
false - increase
What are the mechanical determinant properties of cartilage?
type (e.g. hyaline), structural composition (i.e. Type I vs II), proportions of structural components (i.e. eater, collagen, elastin, proteoglycans)
Which of the following is not true for cartilage?
a. anisotropic
b. biphasic
c. capable of large visoelastic deformation
d. injury/pain is felt immediately
d - injury can often occur without initial awareness and can progress until tissue destruction is quite advanced before pain is experienced
What are the mechanical determinant properties of bone?
size, density, and geometry;
mode of loading applied;
rate and frequency of loading
What are the mechanical properties of cortical bone?
very high ultimate strength in compression and tension,
very high stiffness,
Fx’s @ ~2% strain,
stiffness and ultimate load increase with increased speed of loading
What are the mechanical properties of cancellous bone?
mod to low ultimate strength depending on porosity,
moderate to low stiffness,
anisotropic,
Fx’s @ ~ 7% strain but can sustain as high as 75% before failure in some instances,
stiffness and ultimate load tolerance increase with increased speed of loading
True/False: Changes in the mech. properties of bone generally parallel changes in bone mass.
true
Where are the stresses on bone from?
WBing and muscle loading
What type of tension does a dynamic splint provide?
spring-loaded = aids in restoration of knee ext
What occurs during static progressive splinting?
apply torque as close to EoR as possible, stress-relaxation, force required to maintain decreases over tine and then adjust to new setting to progress
What are some clinical scenarios to utilize open chain exercise?
OA, NWBing, ligament tear, cartilage
What are some clinical scenarios to utilize closed chain exercise?
strength, function, bone remodeling (compression), motor unit activity (= increased muscle effort around a joint)
Delayed onset muscle soreness is due to what phase of contraction?
eccentric
