Module 2: articular structure and pathology Flashcards
What as the synovial joint comprised of?
Joint capsule
Joint space
Synovial fluid
articular cartilage
What are the 2 parts of the joint capsule?
- Fibrous joint capsule
2. Synovial membrane (inner layer)
What is the outer layer of the joint capsule called?
Fibrous capsule (stratum fibrosum)
Fibrous capsule is ____ in blood supply and ____ in joint receptors.
Poor in blood supply but rich in joint receptors
What is the inner layer of the joint capsule called?
synovium
What 2 types of cells exist in the synovium?
Type B and Type A
What is the function of the Type B cells of the synovium?
Synovial fluid production
What is the function of the Type A cells of the synovium?
Immune function
What do Type B cells in the synovium secrete?
HA (hyaluronate/hyaluronic acid): Gel to improve viscosity of fluid-attracts H2O
Lubricin: Reduce friction of the joint
What do Type A Cells in the synovium secrete?
Immunoglobulins
lysosomal enzymes
lyse debris
What does the term Thixotropic properties refer to?
viscosity varies inversely with velocity of movement
at rest the synovial fluid _____ movement of the joint?
resists
At movement synovial fluid _______ ____ ____ to movement
provides less resistance
What is the function of the hyaline cartilage that covers the ends of most bones?
reduce friction
absorb/disperse
compressive forces
What is the cellular component of the articular cartilage?
Chondroblasts (chondrocytes)
What is the function of the chondrocytes?
produce and maintain extra-cellular matrix
Secrete enzymes that assist in matrix
Forms 2% of cartilage
What are the components of the extra-cellular matrix of the articular cartilage?
non-fibrous
Fibrous
What is the non-fibrous component of the articular cartilage extra cellular matrix, made up of?
Primarily water (60-80%)
Protein, proteoglycans (5-10%)
regulates fluid flow in/out of cartilage
What is the fibrous component of the articular cartilage extra cellular matrix made up of?
Collagen fiber (10-30%) TYPE 2 COLLAGEN arranged to abosorb mechanical stress
The fibrous component of the matrix is made up of collagen that is arranged to absorb mechanical stress. Describe Zone 1 of the cartilage bone interface:
Smooth surface
Reduce friction of joint surface
The fibrous component of the matrix is made up of collagen that is arranged to absorb mechanical stress. Describe Zone 2&3 of the cartilage bone interface:
transitional zones, absorb compressive forces
The fibrous component of the matrix is made up of collagen that is arranged to absorb mechanical stress. Describe Tidemark of the cartilage bone interface:
Interface between uncalcified and calcified layers
The fibrous component of the matrix is made up of collagen that is arranged to absorb mechanical stress. Describe Zone 4 of the cartilage bone interface:
Calcified cartilage, anchors cartilage to bone
What mediators all play a role in maintaining matrix turnover?
Enzymes
Hormones
Mechanical stimuli
Where are enzymes secreted from and what role do they play in matrix turnover?
Chondrocytes
assist in breakdown and rebuilding matrix
What hormones stimulate chondrocytes in the matrix?
GH and IGF
What occurs to fluid in the synovial space during weight bearing?
Fluid is pushed out of cartilage
when flow becomes slower cartilage is compressed as the resistance becomes exponentially harder.
What is responsible for the regulation of fluid flow in/out of cartilage?
Proteoglycans
What occurs to fluid in the synovial space when non-wt bearing?
Fluid is allowed to re-enter back into cartilage
What is the purpose of the synovial fluid cycle of wt bearing vs. non wt bearing?
allows fluid to enter and exit the space and carry nutrients
Does articular cartilage have nerve supply?
no
Does articular cartilage have blood supply?
no
Where does the pain in an articular cartilage injury come from?
inflammation/swelling/irritation of surrounding tissue.
How well does articular cartilage regenerate?
very poorly.
Not a lot of blood supply
Osteoarthritis is considered what type of disease? Inflammatory/non-inflammatory?
non-inflammatory but does have an inflammatory component to it.
what is the MC joint disease?
Osteoarthritis
What is the primary defect of OA?
loss/disruption of articular cartilage
disruption of matrix
What gross articular cartilage changes can be seen in OA?
Smooth glossy surface becomes dull yellow/brown gray color with surface flaking fissures and fibrillations
What do the cellular changes that occur during OA lead to?
Enzymatic changes
Hormones insensitivity
Cytokines excess
Nitric Oxide apoptosis
what enzymatic changes occur during OA?
Excess enzyme secreted from chondrocytes leading to matrix breakdown
What is responsible for the movement of synovial fluid?
proteoglycans
What is broken down by lytic enzymes in OA resulting in loss of fluid regulation?
Proteoglycans, collagen and glycoaminoglycans
What is normally found but is found in excess in the synovial fluid during OA?
PTGs
What hormonal changes occur during OA?
decreased chondrocyte sensitivity to IGF and GH
what agent is not normally found in the synovial fluid but is found in the synovium of pt’s with OA?
Nitric oxide
What does NO in the synovium facilitate?
Chondrocyte death (apoptosis)
What is the primary disruption of the articular cartilage matrix in OA?
fluid flows in/out easier due to disruption
What occurs to fluid during rest in OA?
Increased volume of water in the cartilage
During wt bearing activity with OA what occurs to the fluid?
fluid is pushed out too rapidly, cartilage is compressed without much resistance
What is the net result of OA on the articular cartilage?
Limits the ability to absorb forces and provide adequate nutrients to chondrocytes
What effect might OA have on surrounding structures of the articular cartilage?
Subchondral bone sclerosis and cuts
Osteophyte formation
Synovial thickening
What are the primary risk factors for OA
trauma
genetics
What is the typical pain that a pt with OA will complain of?
Morning pain/following prolonged postural positions
relief with easy activity increased with extreme
Referred pain in spine for entrapment
Tx of OA: conservative care:
appropriate exercise
joint mobility
lifestyle changes
Tx of OA: Pharmaceutical
targeted symptomatic relief (OTC-narcotics)
Tx of OA: Surgical:
Viscosupplementation (Hyaluronic injection-joint fluid therapy)
Only approved for the the knee
TX of OA: Cartilage “repair” strategies
Arthroscopic lavage
Marrow stimulating technique (microfractures)
Osteochondral autographs and allographs (OATS)
Cell-based repair
