Cartilage Flashcards
How is compressive force expressed?
kg/cm^3
What is the compressive threshold for cartilage injury?
20-26 kg/cm^3
Excessive unit loads on cartilage lead to…
damage of articular cartilage
(too much pressure can kill chondrocytes, can’t regenerate cartilage)
What protects the joint cartilage from exceeding unit load?
- MC adjacent mm & tendons
- extra-articular ligaments
- joint & bone deformation (cartilage; bony curvatures)
- intra-articular structures (ligaments, menisci)
Name 3 external support structures of a joint
- tendons
- ligaments
- muscles
What are the 3 types of articular cartilage?
- hyaline cartilage
- fibrocartilage
- elastic cartilage
What type of collagen is found in hyaline cartilage?
type 2 collagen
What is fibrocartilage composed of?
type 1 collagen
What is elastic cartilage composed of?
type 2 collagen + elastin
What type of joints have hyaline cartilage?
synovial jts
rib cartilages
Type 2 collagen resists ____ forces
compressive
Type 1 collagen resists ____ forces
tensile
What is the weakest type of cartilage?
hyaline
What type of cartilage is susceptible to chondral fractures from tensile forces?
hyaline
(sideways forces eg. varus/valgus force on knee)
What is an osteochondral fracture?
a break in cartilage and subarticular bone
What type of cartilage resists tensile forces?
fibrocartilage
What types of joints have fibrocartilage?
symphyseal jts & special cartilages
Menisci are composed of what type of cartilage?
fibrocartilage
The glenoid and acetabular labrums contain what type of cartilage?
fibrocartilage
What type of cartilage is between the distal radioulnar joint and the carpals?
(triangular) fibrocartilage
What is the strongest type of cartilage?
fibrocartilage
What is the most flexible type of cartilage?
elastic
Where is elastic cartilage found?
(not generally articular)
- pinna of ear
- eustacian tube
- epiglottis
What type of cartilage helps to “clear” ears?
elastic
What is hyaline cartilage composed of?
- chondrocytes
- ECM
What makes up the extracellular matric of hyaline cartilage?
- 70-80% water
- 20-30% type 2 collagen & proteoglycans
- trace amounts of lipids, phospholipids & lysozymes
What gives the shock-absorbing capability of hyaline cartilage?
fluid (70-80% water)
What draws water into hyaline cartilage?
proteoglycans are hydrophilic
What proteoglycan is found in the nucleus of intervertebral discs that accounts for shock absorption?
chondroitin sulfate (strongly hydrophilic)
What accounts for the decreased shock absorption of the intervertebral discs as we age?
chondroitin sulfate is converted to keratin sulfate which is less hydrophilic
What are the functions of hyaline cartilage?
- shock absorption
- lower coefficient of friction (near 0)
Generally, hyaline cartilage should be no thicker than ____, because…
- 6mm
- obtains nutrients via diffusion, needs to be thin
Why would patients with Acromegaly have degenerative changes in their joints?
thickened cartilage reduces diffusion of nutrients
How does healthy hyaline cartilage create a coefficient of friction near 0?
- smooth, glass-like surface
- covered by synovial fluid (no ^heat)
What happens to the coefficient of friction in degenerative arthritis?
increases (^friction, ^heat)
