Limits of the MSK System - Cartilage Flashcards
state 3 functions of articular cartilage
1) transfers forces between articular joints
2) distributes force within a joint
3) allows relative movement between articular surfaces with minimal friction
how is cartilage made up?
1) cells (5-10% of cartilage)
- chondrocytes
2) intracellular metric (90-95%)
- water (65-80% of IM)
- structural macro molecules (20-35% IM) (type 2 collagen and proteoglycans)
state 3 additional characteristics about cartilage
1) avascular (no blood supply)
2) aneural (no nerves)
3) synovial fluid (essential to the healthy function of the synovial joint)
what is collagen ?
collagen is the structural framework of cartilage, tendons, and ligaments
what are the functions of collagen ?
1) provides tensile stiffness and strength
2) has little resistance to compression or shear
3) arranged to exploit tensile strength
what is the tensile strength of collagen ?
100 MPa (like nylon)
explain the 3 layers of collagen
1) close to bone is perpendicular to the bone - prevents collagen being pulled away from bone via tensile forces
2) at articular surface is oriented parallel to the surface - prevents collagen being pulled sideways - keeps shape of cartilage - allows friction free movement
3) in the middle - randomly aligned - is a framework for proteoglycans
state 3 characteristics of Proteoglycans
1) give cartilage its viso-elastic properties (dependent on the rate at which force is applied)
2) highly negative electrostatic charge (same as each other) keeps stiffness as want to repal each other
3) hydrophilic - draws water into material - keeps plump and cushiony
state the 4 physical properties of cartilage
1) tensile properties
2) compressive properties
3) shear properties
4) viso-elastic properties
state 2 facts about the tensile properties of cartilage
- determined by the arrangement of collagen
- tensile strength higher parallel to surface than perpendicular
state 2 facts about the compressive properties of cartilage
- determined by the proteoglycan content
- compressive stiffness less at surface and greater in the middle zones
state 2 facts about the shear properties of cartilage
- provided by the arrangement of collagen
- resistance to being pulled side to side
state 3 facts about the visco-elastic properties of cartilage
- associated with the flow of water in to the muscle
- the higher the pressure and compressive strains, the less permeable the cartilage becomes
- display ‘creep’
what 2 reasons makes mechanical loading and unloading essential for cartilage health
1) influx of nutrients
2) efflux of waste product
state 2 facts about cartilage remodelling
1) remodelling response occurs when the cartilage is damaged, but is very limited
2) chondrocytes synthesis new matrix components, but fail to restore matrix to normal, even if the damage is minimal
state the two causes of acute cartilage failure
1) active forces (i.e. - heavy lifting)
2) impact forces (i.e. - collisions)
state the 2 causes of chronic cartilage failure
1) interfacial wear caused by a lack of lubrication I abnormal or degenerative joints
2) fatigue wear (occurs when proteoglycan-collagen matrix is damaged by cyclical stressing)
state 2 additional facts about how ‘fatigue wear’ leads to chronic failure of cartilage
- caused by the application of high active or impact forces over a long period of time (e.g. - running)
- important factors are magnitude/intensity of stress, loafing frequency, and duration
state what it is meant by the key term - ‘osteoarthritis’
osteoarthritis is a degenerative condition of cartilage and the underlying bone
where is osteoarthritis most common?
hip, knee, lower back, and fingers
what is the incidence rate of osteoarthritis in those aged 60 and above?
15%
what is the thought cause of osteoarthritis?
thought to be caused by mechanical stress with insufficient wear of the tissue
when is osteoarthritis most likely?
when sportspeople have had a previous injury to that area
state 3 treatments for osteoarthritis
1) lifestyle/gait modification
2) pain medication
3) joint replacement (includes partial joint replacement)
state what it is meant by the key term - menisci
menisci are fibrocartilage semi-lunar discs located between the tibial and femoral condyles and are connected by a transverse ligament
state 2 functional properties of the menisci
- increase the connectivity of the tibial plateaus
- distribute load in the knee over a large surface area and play a key role in shock absorption
state 2 additional facts about the menisci
- thickest part at the peripheral boarders and then taper down towards the middle
- medial menisci merges with the joint capsule and the medial collateral ligament
state 4 facts about menisci injuries
1) associated with ligament injuries at the knee
2) result in mechanical constraint to movement
3) occur due to wear and tear or acute damage
4) most common acute damage is due to ligament damage (medial collateral ligament is connected to the medial menisci)
explain the basic physics behind an MRI scan (3 points)
1) strong magnetic field align the protons in H2O in the body
2) perpendicular magnetic field pulses at different frequencies to disturb protons from alignment
3) different tissues of the body re-align at different speeds emitting different radio frequencies
what radiation is an MRI scan ?
non-ionising radiation
what type of image does an MRI scan produce?
3D imaging
much greater contrast of different soft tissue injuries than CT
what reasons could make MRI not possible for all patients ?
- pacemaker
- stimulator implant
- claustrophobia (most common)
state 4 facts about Arthroscopy (keyhole surgery)
1) a structural technique for viewing inside of joints
2) invasive - only done of there is a known problem which needs fixing
3) minimally invasive way of solving a problem - but with minimal view
4) surgeon can manipulate what is going on in the joint
state 4 facts about the repair of cartilage
1) chondrocytes can regenerate new proteoglycans and matrix
2) avascular - no blood supply
3) cannot regenerate to the same degree as before
4) damage occurring is faster than remodelling so accumulates over time - cartilage is most likely to degenerate out of the tissues in the MSK system
