Pathophysiology of Bone + OA

Question 1

What are the functions of bone?

Answer 1

Structural = support, protection + movement
Mineral storage = calcium + phosphate
Lipid storage
Blood cell formation

Question 2

What are the different types of bones?

Answer 2

Long bone
Short bone
Flat bone
Irregular bone

Question 3

Describe a long bone

Answer 3

Long shaft + 2 distinct ends
Compact bone on exterior with spongey inner bone marrow

Question 4

What is an example of a long bone?

Answer 4

Humerus, femur

Question 5

Describe a short bone

Answer 5

Roughly cube-like
Thin compact bone layer surrounding spongy bone mass

Question 6

What is an example of a short bone?

Answer 6

Carpal + tarsal bones

Question 7

Describe a flat bone

Answer 7

Thin, flattened + usually curved
Parallel layer compact bone with spongy layer between

Question 8

What is an example of a flat bone?

Answer 8

Sternum, skull, ribs

Question 9

Describe an irregular bone

Answer 9

Complicated shapes
Consist of spongy bone with thin layer of compact

Question 10

What are the 2 major types of bone?

Answer 10

Compact bone = stronger, dense, NOT porous
Cancellous bone = spongy

Question 11

Describe a compact bone

Answer 11

Mechanical + protective
Dense bone tissue on outside of bone
Enclosed + covered by periosteum

Question 12

Describe a cancellous bone

Answer 12

Interior = fibres + lamellae
Metabolic Ca regulation
Storage
Stem cells

Question 13

LEARN long bone gross anatomy

Answer 13

LOOK AT LECTURE

Question 14

What does red bone marrow do?

Answer 14

Supplies nutrients to osteoclasts
Forms red + white blood cells

Question 15

What does yellow bone marrow do?

Answer 15

Stores fat

Question 16

What are the 4 main types of bone cells?

Answer 16

Osteoprogenitor
Osteoblasts
Osteocytes
Osteoclasts

Question 17

What is the function of osteoprogenitor?

Answer 17

Develop into osteoblasts

Question 18

What is the function of osteoblasts?

Answer 18

Bone building
Differentiate into osteocytes

Question 19

What is the function of osteocytes?

Answer 19

Form osteoblasts

Question 20

What is the function of osteoclasts?

Answer 20

Bone crushing

Question 21

What is the mechanism of bone remodelling?

Answer 21

Response of osteocytes to microdamage
Signalled by growth hormones/cytokines
Bone surface populated with osteoclast precursors
Osteoclast + osteoblasts recruited
Osteoclasts mature + remove mineralised bone
Osteoclast numbers decline + replaced by osteoprogenitor cells
Osteoprogenitor = osteoblasts = collagen = mineralisation

Question 22

Describe the method of osteoclast resorption

Answer 22

Osteoclast adheres to bone = secretes HCl + proteases

Question 23

What is osteoarthritis?

Answer 23

Degenerative disorder of joints, causes significant pain + disability

Question 24

Where is osteoarthritis usually located?

Answer 24

Knee
Hip
Spine
Small joints of hand

Question 25

What are the risk factors for OA?

Answer 25

Obesity Increasing age

Question 26

What is the cause of primary OA?

Answer 26

Idiopathic

Question 27

What is the cause of secondary OA?

Answer 27

Previous injury to joint Inflammatory arthritis (gout/RA)

Question 28

What is the pathophysiology of OA?

Answer 28

Imbalance between joint repair + destruction Joints subjected to large load/impact = cartilage + bone strain + damage Rate of damage > rate of repair Cartilage progressively destroyed = narrowing of joint space + overgrowth of bone = inflammation of synovial lining + swelling of joint

Question 29

What is OA characterised by?

Answer 29

Breakdown of articular cartilage + proliferative changes of surrounding bones

Question 30

What are the risk factors of OA?

Answer 30

>50 Female BMI >25 Previous injury Laxity of joint ligaments Occupational/recreational use of affected joint Family history

Question 31

What happens with OA?

Answer 31

Thinned cartilage = bone ends rub together

Question 32

What is the diagnosis of OA?

Answer 32

No validated diagnostic tool Pain symptoms with physical joint findings in patients with risk factors OA features can be seen on a x-ray

Question 33

What OA features can be seen on a x-ray?

Answer 33

Space narrowing Bone spurs Subchondral sclerosis Subchondral cysts

Question 34

What are Heberden's nodes?

Answer 34

Hard bony swelling on distal interphalangeal joints at end of fingers

Question 35

What are Bouchard's nodes?

Answer 35

Hard bony cysts occurring on proximal interphalangeal joints

Question 36

What is the most common location of OA?

Answer 36

Knee joint

Question 37

Describe the pain with OA in knee

Answer 37

Activity-related Worse at end of day Symptoms may be episodic + vary in severity

Question 38

What is the second most common location of OA?

Answer 38

Hip

Question 39

What are the risk factors for hip OA?

Answer 39

Obesity Employment with lifting heavy objects Physical work Sport - eg. running

Question 40

What is common in patients with hip OA?

Answer 40

Difficulty moving hip joints = putting shoes + socks on = getting in + out of car = going up + down stairs

Question 41

What is the molecular pathophysiology of OA?

Answer 41

Chondrocytes generate matrix degradation products + proinflammatory mediators for repair = stimulate chondrocyte + proliferation = increased vascularity + vascular invasion = increased bone turnover + subchondral bone marrow lesions Osteophytes form at joint margins

Question 42

Describe the symptoms of OA

Answer 42

Pain Morning stiffness Joint swelling Reduced range of motion + muscle weakness Crepitus of joints Joint instability Fatigue Pain-related psychological stress

Question 43

Describe treatment of OA

Answer 43

1st line = paracetamol/topical NSAID Adjuncts = capsaicin cream/intra-articular corticosteroids Ineffective = add in OR substitute Add in/substitute = NSAID + PPI