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MSK > Physiology of Joints > Flashcards

Physiology of Joints Flashcards

1
Q

what are the three types of joint in the body

A

synovial
fibrous
cartilaginous

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2
Q

describe fibrous joints (synarthrosis) and give an example of one

A

when bone are united with fibrous tissue, dont allow movement

bones of the skull in adults

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3
Q

describe cartilaginous joints (amphiarthrosis) and give 5 examples

A

bones united by cartilage, allow little movement

intervertebral discs
pubic symphsis
part of the sacroiliac joints
costochondral joints

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4
Q

describe synovial joints (diarthrosis)

A

when bones are separated by a cavity (containing synovial fluid) and united by a fibrous capsule (+ other extra articular structures: ligaments, tendons and bursae)

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5
Q

what lines the inner aspect of a synovial fibrous capsule

A

synovial membrane (60 microM thick)

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6
Q

what is the synovial membrane

A

vascular connective tissue with capillary networks and lymphatics

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7
Q

what does the synovial membrane contain that produces synovial fluid

A

fibroblasts (synovial cells)

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8
Q

what covers the articular surfaces of bones in synovial joints

A

cartilage

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9
Q

describe the two types of synovial joints

A

simple- one pair of articular surfaces

compound- more than one pair of articular surfaces (e.g elbow)

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10
Q

what extra articular surfaces support joints

A

ligaments, tendons and bursae

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11
Q

what are the physiological functions of joints

A

to serve the functional requirements of the MKS

structural support and purposeful movement

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12
Q

what is an additional role of the joint during purposeful movement

A

stress distrubution

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13
Q

how does the joint remain stable

A

the shape of the articular component

ligaments stabilise

synovial fluid acts as an adhesive seal that freely permits sliding motion between cartilaginous joints

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14
Q

what provides joint lubrication

A

cartilage interstitial fluid

synovium- derived hyaluronic acid (mucin- a polymer of disaccharides)

synovium- derived lubrcin (a glycoprotein)

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15
Q

what are the 6 roles of synovial fluid

A

lubricates joint

facilitates joints movements (reduced friction)

help minimise wear and tear

aids in the nutrition of articular cartilage

supplies the chondrocytes (cartilage cells) with O2 and nutrients

removes Co2 and waste products

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16
Q

what does the synovial fluid fill

A

the joint cavity

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17
Q

is the synovial fluid a static pool- explain

A

no- synovial fluid is continuously replenished and absorbed by the synovial membrane

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18
Q

why does synovial fluid have a high viscosity

A

due to the presence of hyaluronic acid (mucin) produced by the synovial cells

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19
Q

does the viscosity of synovial fluid vary

A

yes, with joint movement

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20
Q

what role does the blood play in synovial fluid

A

constituents such as uric acid are derived from by dialysis of blood plasma

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21
Q

what cells are contained within the synovial fluid

A

not many- mostly mononuclear leucocytes

<200 WBC/mm3 (0f which polymorphs are usually <25/mm3)

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22
Q

what happens to the synovial fluid during joint movement (especially rapid movement)

A

the viscosity and elasticity change

rapid movement=
viscosity descreased
elasticity increased

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23
Q

what properties of synovial fluid become defective in diseased joints (e.g. osteoarthritis)

A

its ability to decrease in viscosity and increase in elasticity during rapid movement

24
Q

what does synovial fluid look like

A

clear and colourless

25
Q

when does synovial blood count increase from more than <200WBC/mm3

A

in inflammatory and septic arthritis

26
Q

when does synovial fluid turn red

A

in traumatic synovial tap and in haemorrhagic arthritis

27
Q

when does synovial fluid go straw to yellow colour

A

inflammatory synovial fluid

28
Q

when does synovial fluid go opaque

A

septic synovial fluid

29
Q

when, other than during movement, is synovial viscosity low

A

inflammatory synovial fluid

30
Q

when is synovial fluid total cell count highest

A

septic synovial fluid

31
Q

what are the roles (2) of articular cartilage

A

provides a low friction lubricated gliding surface which helps prevent wear and tear of joints

distributes contact pressure to subchodral bone

32
Q

what plays a key role in determining the mechanical properties of cartilage

A

the composition of the cartilage ECM and the interaction between the fluid and solid phase of the cartilage

33
Q

list the different zone of articular cartilage from outwards to inwards

A 
articular surface 
superficial zone 
middle zone 
deep zone 
calcified zone 
(subchondral bone)
34
Q

what do the zones of articular cartilage differ in

A

organisation of collagen fibres and relative content of cartilage components

35
Q

what type of cartilage is articular cartilage usually

A

hyaline

36
Q

describe the properties of articular cartilage

A

elastic and spongey

37
Q

what parts of bone does the articular cartilage cover

A

articular surfaces

38
Q

what makes up the extracellular matrix of articular cartilage

A

water (70%)
collagen (20%, mainly type II, contributes to the elastic behaviour)
proteoglycans (10%)

39
Q

describe 4 key properties of water in cartilage

A

70% of cartilage wet weight

unevenly distributed, 80% near articular surface

content decreases with age

maintains the resiliency of the tissue and contributes to the nutrition and lubrication system

40
Q

describe 5 key properties of collagen in cartilage

A

20% of wet weight

mainly type II

decreases with age

maintain cartilage architecture

provides tensile stiffness and strength

41
Q

describe the 5 key properties of proteoglycan

A

10% of cartilage wet weight

highest concentration in middle and deep zone

composed mainly of glycosaminoglycan e.g. chondroitin sulphate

composition changes with age (chondroitin decreases with age)

responsible for the compressive properties associates with load bearing

42
Q

how much of cartilage volume is ECM (extracellular matrix)

A

> 98% of cartilage volume

43
Q

what synthesises, degrades and maintains the ECM

A

chondrocytes (usually <2% of the total cartilage volume)

44
Q

how does articular cartilage and chondrocytes receive nutrients and O2

A

articular cartilage is avascular- gets it from synovial fluid

45
Q

how does the rates of ECM degradation and replacement compare in normal joints

A

degradation doesn’t exceed replacement

46
Q

how do chondrocytes degrade ECM components (e.g. collagen and proteoglycan)

A

metalloproteinase PROTEOLYTIC ENZYMES

e.g. collagenase and stomelysin

47
Q

what can change the mechanical properties of the knee

A

changes in the relative amounts of the components (water, collagen and proteoglycans)

or

if ECM degradation exceed rate of synthesis

48
Q

what do the catabolic factors of cartilage matrix turnover do, give 2 examples of them

A

stimulate proteolytic enzymes and inhibit proteoglycan synthesis

TNF alpha
Interleukin - 1

49
Q

what do the anabolic factors of cartilage matrix turnover do, give 2 examples of them

A

stimulate proteoglycan synthesis and counteract effects of IL-1

tumour growth factor (TGF- beta)
insulin like growth factor (IGF-1)

50
Q

what are the two markers of cartilage degradation and why are they present

A

serum and synovial keratin sulphate

  • increased levels indicate cartilage breakdown
  • level increses in patients with osteoarthritis

type II collagen in synovial fluid

  • increased levels indicate cartilage breakdown
  • useful in evaluating cartilage erosion (e.g. in osteoarthritis and rheumatoid arthritis)
51
Q

what is osteoarthritis caused by

A

cartilage and synovial composition and function deteriorate with age and repeated wear and tear

52
Q

what causes rheumatoid arthritis

A

synovial cell proliferation and inflammation

53
Q

what causes gouty arthritis

A

deposition of salt crystals (e.g. uric acid) in the joint

54
Q

what causes soft tissue rheumatism

A

injury and inflammation to periarticular structures (e.g. injury to tendon causes tendonitis

55
Q

what effects on the bone can be seen following cartilage wear and tear

A

cyst formation
sclerosis in subchondral bone
osteophyte formation

56
Q

what shaped needles in gouty arthritis

A

needle shaped

57
Q

what type and shape of needles in pseudo gout

A

rhomboid shaped calcium pyrophosphate crystals

MSK (71 decks)

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