Studied by 80 peopleWhere is fibrocartilage found?
Found inside of joint (can divide the joint into two functional units)
What type of collagen is most prominent in fibrocartilage?
Type I collagen (chondrocytes synthesize and secrete this)
What are the roles of fibrocartilage?
Increase joint congruency
Assist with joint lubrication
Protect edges of joint
Act as a shock absorber
Act as load bearers (transmit loads)
In normal, healthy tissue, menisci should be ________, ________, and ________
In normal, healthy tissue, menisci should be smooth, glistening, and intact
According to Dr. Evans’ slides, the meniscus is a ________ tissue
According to Dr. Evans’ slides, the meniscus is a substantial tissue
What type of shape is the meniscus? Where does it attach?
Semi-lunar structure that attaches to the tibial plateaus
When is the meniscus susceptible to injury?
During loaded, rotational activities (sports)
What is the function of the meniscus?
Acts as a buffer to the articular structures
Dampens impact (like a shock absorber)
Increases stability of the joint
Distributes load
Protects the articular cartilage and bony surfaces
The meniscus is responsible for __% of the load in the knee
The meniscus is responsible for 70% of the load in the knee
Meniscus removal leads to increasing _________ load by about __ times.
Meniscus removal leads to increases compressive loads by about 5x
Without the menisci, what happens to the load? Where does the area of loading become?
Load becomes more localized with smaller surface area
Area of loading becomes the center of the tibial plateau
What components of the load are affected by menisci?
Magnitude and distribution of the load are affected by menisci
The ability of menisci to form a _______ matrix is dependent upon ________.
The ability of menisci to form a solid matrix is dependent upon permeability
If permeability of the meniscus increases, what happens to its efficacy?
Meniscus is less effective
T/F: There is a linear relationship of menisci thickness to articular cartilage
False! They have an inverse relationship; where one is thick the other is thinner
(e.g., outer edge meniscus is MUCH thicker so the articular cartilage is very thin)
What % of meniscus structure is water?
70% water
Proteoglycans account for __% of the dry weight of the meniscus
Proteoglycans account for <10% of the dry weight of the meniscus
For the meniscus, collagen is about ____% of organic solids (type I)
For the meniscus, collagen is about 60-90% of organic solids (type I)
T/F: Menisci are aneural and void of lymphatics
True
Where is the vascular supply located for the meniscus?
Along the periphery (outer 1/3)
T/F: Pain does not come from the meniscus
True
T/F: Menisci tissue is anisotropic
True!
T/F: There is significantly more proteoglycans in the menisci than articular cartilage
False! There is significantly less proteoglycans in the menisci (indicating that it is a fiber rich structure)
What are the cells of the meniscus called?
Fibroblasts (very few of them)
What is the “red zone” of the meniscus?
Vascular portion / outer region of the meniscus
The “red zone” of the meniscus is made up of about __% dry weight type __ collagen
The “red zone” of the meniscus is made up of about 80% dry weight type I collagen
What are the cells like in the “red zone” of the menisci?
Cells are spindle-shaped and are more “fibroblastic-like” (it behaves kind of like lig/tendon)
What is the “white zone” of the meniscus?
Avascular / inner region of the meniscus
The “white zone” of the meniscus is made up of __% collagen. What percentage of that is type I and type II?
The “white zone” of the meniscus is made up of 70% collagen.
60% of that is type II (majority)
40% is type I
T/F: The “white zone” of the menisci contains a greater portion of proteoglycans
True! (mostly aggrecan, but also biglycan and decorin)
What are the cells like in the “white zone" of menisci?
Cells are more chondrocyte-like (they behave more like articular cartilage)
The superficial layer of the meniscus has what type of cells? What is their purpose/function?
Small and round cells — they disperse tensile load
What are the three layers of collagen fibers?
Superficial Layer
Intermediate Layer
Inner-Most / Deep Layer
What is the type and arrangement of the collagen fibers in the superficial layer?
Fine collagen fibrils (predominately type I)
Randome woven matrix
The intermediate layer is approximately ___ microns from the surface
The intermediate layer is approximately 100 microns from the surface
What is the arrangement of the intermediate layer?
Collagen bundles are large, rope-like
Arranged circumferentially around the semilunar meniscus
Smaller, radial fibers reinforce the structure by tying the larger fiber bundles together
Radial fibers (located in the intermediate layer) have a higher ______ modulus/strength.
Radial fibers (located in the intermediate layer) have a higher tensile modulus/strength.
In the intermediate layer, what fibers detect the compression force?
Radial fibers
What is the arrangement like in the inner-most / deep layer?
Randomly arranged fibers
More proteoglycans
(more “articular cartilage like”)
When considering the layering of collagen fibers, the outside looks like ________ and the inside looks like ________.
When considering the layers of collagen fibers, the outside looks like tendon/ligament and the inside looks like articular cartilage
If compression is applied, it will cause a ______ force across the surface — the ______ fibers are being pulled and create ______ and the __________ fibers place pressure on the 3rd layer.
If compression is applied, it will cause a tensile force across the surface — the radial fibers are being pulled and create tension and the circumferential fibers place pressure on the 3rd layer
Circumferential fibers and radial fibers are part of which layer?
Intermediate / 2nd layer
T/F: The medial and lateral menisci are essentially the same in their arrangement
False!
Describe the arrangement of the lateral meniscus.
Has the same arrangement throughout (e.g., same arrangement in posterior horn and anterior horn, etc.)
Type I collagen fiber bundles that are highly oriented parallel to the periphery of the tissue
Describe the arrangement of the medial meniscus.
Collagen bundles have significantly less circumferential organization in the posterior aspect
In which meniscus (medial/lateral) does more injury tend to occur?
Medial meniscus
Considering the arrangement and organization of the medial and lateral menisci, what does this mean regarding the forces they receive?
Lateral aspect gets more compressive forces
Medial aspect gets more gapping
Think about standing and how we have knee valgus
How does the meniscus receive nutrients?
Fluid flow in and out of tissue during cyclic compression
Weeping is occurring but not to the extent that is seen in articular cartilage
The meniscus is more/less permeable than articular cartilage?
The meniscus is less permeable than articular cartilage
Where is the magnitude of compressive loading the greatest on the menisci?
Superior surface of both medial and lateral menisci
Along the central “strip” of each structure
Load bearing capacity is greater in which meniscus (medial/lateral)?
Greater in the lateral meniscus (because it is more organized and behaves with hoop stress)
Normal knee motion is typically describing the meniscus as…
Bending with knee flexion
The meniscus has properties of an __________ solid
The meniscus has properties of an incompressible solid
What percent of the population has direct attachment with the posterior horn of the lateral meniscus via the oblique popliteal ligament?
50%
The meniscus, in general, has a lower _______ modulus and a higher _______ modulus
The meniscus, in general, has a lower compressive modulus and a higher tensile modulus
T/F: The stress-strain curve of the meniscus is not truly linear
True
What does it indicate if a stress-strain curve is not linear?
Indicates that all stresses can cause plastic deformation
Failure of the meniscus occurs at ____% elongation
Failure of the meniscus occurs at 25-40% elongation
How does the anterior portion and the posterior portion of the menisci differ in terms of their stress-strain relationship?
Anterior portion fails at higher strain rates but lower stresses than other areas
Posterior meniscus has a lower modulus but a higher max stress
What is hoop stress?
As we know, collagen resists tensile strength
In the meniscus, the collagen are arranged circumferentially
As tensile loads are resisted, the collagen is loaded as hoop stress
In what direction are menisci stiffer?
Menisci are stiffer in the circumferential direction (as opposed to the radial direction)
The medial meniscus (posterior portion) has considerably lower ______ strength and modulus
The medial meniscus (posterior portion) has considerably lower tensile strength and modulus
Where does stress focus on the lateral meniscus? What does this mean?
Stresses focus on the intermediate portion and secondarily on the posterior portion
Means more stress concentration areas (and therefore more susceptible to injury)
Where does the lateral meniscus tend to split?
Intermediate region
Where does the medial meniscus tend to split?
Posterior region
The radial modulus is ___ times lower than the circumferential modulus
The radial modulus is 10 times lower than the circumferential modulus
T/F: When the meniscus tears, the remaining fibers are able to maintain the mechanical functionality required for the meniscus
True!
When the meniscus is injured, how is stress transferred?
Radial “tie” fibers transfers stresses to the remaining intact circumferential collagen fibers
A tear needs to reach about ___% of the meniscus width before tibial contact stresses increase
A tear needs to reach about 90% of the meniscus width before tibial contact stresses increase
Why are cortisone injections not good for a meniscal injury?
Because of the close proximity of the meniscus to articular cartilage
Are NSAIDs okay for a meniscal injury?
May be okay initially, but there are long-term concerns
How long does it take fibrous scar tissue to form? Does it act like fibrocartilage right away?
Take 10 weeks for fibrous scar tissue to form; but it takes months for it to act like fibrocartilage
How would you treat a meniscus with exercise?
Treatment tends to be like articular cartilage
We want some cyclic compression for nutritonal health
The potential for wear (on the meniscus) increases when the joint goes from ______ loading to ______ loading
The potential for wear (on the meniscus) increases when the joint goes from static loading to high loading
(ease into exercise with warm up of joints)
What rate of loading is the most protective?
Moderate rate of loading (more protective than fast or slow)
What is a meniscectomy? What does it lead to?
Removal of part or all of the meniscus
Either will increase the incidence of premature OA secondary to shifting load onto the articular cartilage
What are the cells of the TMJ disc called?
Fibroblasts (few cells)
T/F: The TMJ disc is avascular and aneural
True!
What type of collagen is the TMJ disc mostly made up of?
Majority type I collagen (with some type II fibers — especially centrall)
The intermediate band of the TMJ has a relatively high concentration of _____ for a tissue that has so many _____ oriented collagen fibers
The intermediate band of the TMJ has a relatively high concentration of aggrecan for a tissue that has so many parallel oriented collagen fibers
T/F: The intermediate band looks like a ligament except is has a low percentage of GAGs
False! The intermediate band does look like a ligament but is has a high percentage of GAGs
What does the anterior and posterior band of the TMJ disc “look like”?
Looks like articular cartilage
What is occurring at the TMJ during passive movement?
The superior and inferior lamina of the disk will basically hold it in place and or “leave it in-line with where the mandible articulates with the temporal bone”
You can sort of think of it as ligaments holding it in place
What is occurring at the TMJ during active movement / forceful opening?
Contraction of the lateral pterygoid m.
Elastic properties of lamina primarily maintain control of disc (while the suprahyoids and inf. fibers of lateral ptergoid translate condyle and disc forward)
NOTE - the superior fibers of the lateral pterygoid are able to control the disc (attachment) along with the collateral ligaments on the lateral portion of the disc, but there is controversy whether the superior lateral pterygoid is active during opening)
What is occurring at the TMJ during relaxed opening?
Lateraly pterygoid m. is relaxed
Passive elastic properties of the superior lamina applies as posterior tractive force to maintain the disc within the mandibular fossa correctly
What does the stress-strain curve of the TMJ disc look like?
Looks like the stress-strain curve for tendon or ligament (probably because most of testing has been on intermediate band)
Are viscoelastic properties (hysteresis, creep, and stress relaxation) present in the TMJ disc?
Yes! It is very similar to tendon/ligament
Reaches equilibrium ~5 min
T/F: With the TMJ disc, there is compression only with active motion or closure
True!
T/F: Deformation of the TMJ disc is the same for passive and active motion
False!
Deformation is different in passive vs active motion
Loss of the _______ band seems to lead to _________ of the TMJ
Loss of the posterior band seems to lead to instability of the TMJ
What is the fracture pattern of the TMJ disc?
Holes / tears of bilaminar retro discal tissue
T/F: There is a psychological component to TMJ pain
True!
T/F: Aging also leads to changes of the TMJ disc just like tendon/ligament and articular cartilage
True! (older you get → less healthy it is)
What should exercise / physical therapy be focused on for TMJ disc pain (or injury)?
Focus on minimizing pain
Improving muscular balance (soft tissue mobilization)
Lateral pterygoid muscle strengthening
If we are treating TMJ disc pain with exercise / physical therapy, what should the reps be? Why?
Reps should be less compared to other joints because the TMJ is constantly being used
T/F: Surgery is the best choice of treatment for the TMJ
False!
Surgery is often recommended but outcome studies demonstrate surgery is often the poorest choice of treatment
Intervertebral discs are ___ the height of the spinal column
Intervertebral discs are 1/3 the height of the spinal column
T/F: Intervertebral discs are the largest avascular structure in the body
True!
T/F: Intervertebral discs respond to both high impact loads (running and jumping) and low impact lows (standing and sitting)
True!
What are the two parts of the intervertebral disc?
Composed of the nucleus pulposus and annulus fibrosis
Note 
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