Joints + joint disease

Question 1

What are the 3 main types of joint?

Answer 1

Fibrous
Cartilaginous
Synovial

Question 2

Sutures, gomphosis, and syndesmosis are all which type of joint?

Answer 2

Fibrous joint

Question 3

What’s the difference in contents between primary and secondary cartilaginous joints?

Answer 3

Primary cartilaginous joints - hyaline cartilage only

Secondary cartilaginous joints - hyaline cartilage + fibrocartilage

Question 4

Is the epiphysis a primary or secondary cartilaginous joint?

Answer 4

Primary cartilaginous joint

Question 5

What is the outer layer of hyaline cartilage called?

Answer 5

Perichondrium

Question 6

What do chondroblasts secrete?

Answer 6

Cartilage matrix

Question 7

In what key way do chondrocytes differ from osteocytes?

Answer 7

Chondrocytes can divide and secrete matrix - osteocytes cannot

Question 8

The fibrous layer of the perichondrium is made up of which type of tissue and fibres?

Answer 8

Dense, irregular connective tissue containing type 1 collagen fibres

Question 9

The cellular layer of the perichondrium contains which 2 types of cells?

Answer 9

Chondrogenic cells
Chondroblasts

Question 10

Where do cartilage cells in the articular cartilage receive nutrients from?

Why is this?

Answer 10

Synovial fluid

Perichondrium is absent on articular cartilage

Question 11

What are the 3 main things that make up hyaline cartilage extracellular matrix?

Answer 11

Aggrecan (a proteoglycan)
Water
Type II collagen fibres

Question 12

What is a proteoglycan?

Answer 12

A core protein with glycosaminoglycans side chains attached

Question 13

What are the 2 types of cartilage growth?

Answer 13

Appositional growth
Interstitial growth

Question 14

Describe what is involved in the appositional growth of cartilage.

Answer 14

Chondrogenic cells in the perichondrium differentiate into chondroblasts which then secrete matrix

Question 15

Describe what is involved in the interstitial growth of cartilage.

Answer 15

Chondrocytes divide, forming isogenous groups and secrete matrix

Question 16

What method of growth is seen in articular cartilage and why?

Answer 16

Interstitial growth - articular cartilage lacks a perichondrium so cannot undergo appositional growth

Question 17

What are the 2 main reasons mature cartilage has limited capacity to repair?

Answer 17

Chondrocytes are bound in lacunae - cannot migrate to areas of damage

Avascular

Question 18

Which 2 key processes are involved in the development of osteoarthritis?

Answer 18

Degeneration of cartilage

Disordered repair

Question 19

In the hand, which joints are most commonly affected in osteoarthritis?

Answer 19

Distal interphalangeal joints (closest to tips of fingers) and thumb

Question 20

Osteoarthritis is initiated by injury to which cell type?

Answer 20

Chondrocytes

Question 21

Describe the formation of osteoarthritis.

Answer 21

Chondrocytes divide and increase matrix production - cartilage swells - hypertrophic repair

Accelerated degeneration of ECM by MMPs - degeneration exceeds repair

Splitting and fissuring of the cartilage (fibrillation)

Joint space narrowing

Ulceration + full thickness erosion of cartilage

Bones rub together + become smooth (eburnation)

Thickening of subchondral bone (subchondral sclerosis)

Microfractures through articulating surface allow synovial fluid to form subchondral cysts

Osteophyte formation

Dislodged cartilage and bone form loose bodies in joints

Hyperplasia + fibrosis of synovial membrane + thickening of joint capsule

Question 22

In the development of osteoarthritis, what is the ECM degraded by?

Answer 22

Matrix metalloproteinases (MMPs)

Question 23

In the development of osteoarthritis, which term describes the splitting and fissuring of the cartilage?

Answer 23

Fibrillation

Question 24

How does the joint space change during the development of osteoarthritis?

Answer 24

Joint space narrows

Question 25

What is eburnation?

Answer 25

When bones rub together and become smooth

Question 26

How does the subchondral bone change in the development of osteoarthritis?

Answer 26

Thickens (subchondral sclerosis)

Question 27

In the development of osteoarthritis, microfractures in the articulating surface allow for the formation of what?

Answer 27

Subchondral cysts

Question 28

What are 2 types of nodes seen in osteoarthritis and where?

Answer 28

Heberden's nodes - distal interphalangeal joints Bouchard's nodes - proximal interphalangeal joints

Question 29

Gout is caused by an inflammatory response to what?

Answer 29

Monosodium urate crystals

Question 30

What percentage of gout is primary and secondary?

Answer 30

Primary - 95% Secondary - 5%

Question 31

Uric acid is produced from the breakdown of what?

Answer 31

Purine

Question 32

What is purine broken down into before becoming uric acid?

Answer 32

Xanthine

Question 33

Which particular joint is most susceptible to gout?

Answer 33

1st metatarsophalangeal joint (big toe)

Question 34

Describe the appearance of urate crystals under polarized light.

Answer 34

Negatively birefringent

Question 35

What are the 4 distinct clinical phases of gout?

Answer 35

Asymptomatic hyperuricaemia (no symptoms) Acute intermittent gout Intercritical periods (no symptoms) Chronic tophaceous gout

Question 36

Pseudogout is caused by an inflammatory response to what?

Answer 36

Calcium pyrophosphate crystals

Question 37

Describe the appearance of calcium pyrophosphate crystals under polarized light.

Answer 37

Positively birefringent

Question 38

List the 5 key micro changes seen in osteoarthritis.

Answer 38

Eburnation Subchondral sclerosis Subchondral cysts Osteophytes Loose bodies

Question 39

What colour are gout crystals when parallel to polarised light?

Answer 39

Yellow

Question 40

What colour are pseudogout crystals when parallel to polarised light?

Answer 40

Blue