Cartilage Flashcards
What is the role of articular cartilage?
- Transfers force between articulating bones
- Distributes forces in joints
- Allows relative movement between articular surfaces with minimal friction
What are the characteristics of articular cartilage?
- Cells
- Intercellular matrix
- Avascular
- Aneural
- Synovial Fluid
What percentage of the cartilage are cells and what do they contain?
5-10%
- contains chondrocytes
What percentage of the cartilage are intercellular matrix and what do they contain?
90-95%
- water (65-80%) and structural macro molecules (20-35%)
what are structural macro-molecules
- collagen (type ii)
- proteoglycan
What is collagen?
- structural framework of cartilage, tendon and ligament
- tensile stiffness and strength
- Little resistance to compression
- Exploit tensile strength
What are Proteoglycans?
- Visco-elastic properties (depends on load and rate) - negative electro static charge - attracted to water -reacts to compressive
What are the physical properties of cartilage?
Tensile
Compressive
Shear
Visco-Elastic
Describe Tensile properties of cartilage
- These are determined by the arrangement of collagen
- Tensile strength is higher parallel to the surface than perpendicular
Describe Compressive properties of cartilage
- Determined by proteoglycan content
- Compressive stiffness least at surface and greatest in the middle zones
Describe Shear properties of cartilage
- provided by arrangement of collagen
Describe Visco-Elasticity properties of cartilage
- associated with movement of water in the tissue
- The higher the pressure and compressive strains, the less permeable cartilage become
- Display ‘creep’
What are essential to keep the cartilage healthy?
Mechanical loading and unloading of joints
- Influx of nutrient
- Efflux of waste products
When does the remodelling process begin
When the cartilage is damaged
What is the job of chondrocytes?
-synthesise new matrix components but fails to restore matrix to normal
What is the failure of the cartilage due to?
- Acute
- -> Active forces
- -> Impact forces
- Chronic
- -> Interfacial wear caused by lack of lubrication in abnormal or degenerative joints.
- -> Fatigue wear - occurs when proteoglycan-collagen matrix is damaged by cyclic stressing.
What are the menisci?
Fibrocartilage
- spacer and stabiliser
- shock absorber
What are the basic physics of MRI?
- strong magnetic field aligns the protons in the body
- perpendicular magnetic field pulses at different frequencies
- different tissues of the body re-aligns at different speeds emitting different radio-frequencies
What are the key features of an MRI?
- it is a 3D image of all structures of the body
- much greater contrast of different soft tissues than CT
- Lengthly imaging (40-60mins)
- expensive (350 per scan)
- no ionizing radiation
What patients may not be able to have MRI
pacemaker
Stimulator implant
claustrophobia
What is arthroscopy
Surgical technique for viewing inside patient joints
what are characteristics of an osteoarthritic knee?
- degenerative condition of cartilage and underlying bone
- can occur at any joint on body
- occurs in 15% of 60+ experience
- caused by mechanical stress within sufficient repair
How do you treat osteoarthritis
- Lifestyle modification
- pain medication
- joint replacement
