Joints and joint disease

Question 1

What types of fibre are found in connective tissue?

Answer 1

Collagen (types 1,2 and 3)

Elastin

Question 2

Where are type 1 collagen fibres found?

Answer 2

Bones
Tendons
Ligaments
Dermis
Organ capsules

Question 3

What are the characteristics of cartilage?

Answer 3

Strong 
Flexible 
Rigid 
Smooth surface for free movement 
Shock absorber

Question 4

What are the functions of cartilage?

Answer 4

Articulating surfaces of bones
Growth and development of bones (through endochondral ossification)
Support (e.g. trachea)

Question 5

What are the features of the cartilage extracellular matrix?

Answer 5

Contains aggrecan (a proteoglycan) - acts to resist compressive forces
Contains fibres (collagen and elastin)

Question 6

Where are cartilage cells derived from?

Answer 6

Mesenchymal stem cells –> Chondroblasts (cartilage building cells)–> Chondrocyte (mature cell)

Question 7

How can cartilage grow?

Answer 7

1. Appositional growth

2. Interstitial growth

Question 8

How does appositional growth occur?

Answer 8

Surface layer of matrix is added by chondroblasts in the perichondrium

Question 9

How does interstitial growth occur?

Answer 9

Chondrocytes grow and divide and lay down new matrix
Articular cartilage and endochondral ossification
[Occurs in childhood and adolescence]

Question 10

How does cartilage growth and repair differ with age?

Answer 10

Regeneration is poor after childhood

Large defects involve replacement with dense connective tissue

Question 11

Where is elastic cartilage found?

Answer 11

External ear
Larynx
Epiglottis

[structures that require degree of deformation with ability to regain original shape]

Question 12

What fibres are found in elastic cartilage and what properties do these give?

Answer 12

Elastic fibres
Type II collagen fibres

[Properties of elastic cartilage: strong, flexible and resilient]

Question 13

What is a joint?

Answer 13

Point at which 2 + bones articulate

[no movement required to be classified as a joint]

Question 14

What are the common diseases affecting joints?

Answer 14

Osteoarthritis
Rheumatoid arthritis
Gout

Question 15

How is osteoarthritis characterised?

Answer 15

Loss of articular cartilage with or without loss of bone leading to synovitis (inflammation of the synovium)
Reduces shock absorbing abilities of cartilage

Question 16

Where are type 2 collagen fibres found?

Answer 16

Hyaline cartilage

Elastic cartilage

Question 17

Where are type 3 collagen fibres found?

Answer 17

Structural framework of spleen, liver, lymph nodes, smooth muscle and adipose tissue

Question 18

What are the functions of elastin?

Answer 18

Enable stretch and recoil of tissues

Often mixed with collagen to prevent overstretch

Question 19

Where is elastin found?

Answer 19

[Wide variety of structures]
Walls of large arteries
Lungs
Skin

Question 20

What are the various types of connective tissue?

Answer 20

Loose irregular connective tissue (e.g. glands, part of serrous membrane etc.)
Dense irregular connective tissue (e.g. dermis of skin, sheaths of nerves, capsules of organs)
Specialised connective tissue (e.g. tendons, ligaments, cartilage, adipose tissue, blood etc.)

Question 21

What is the structure of cartilage?

Answer 21

Lined with a perichondrium (that has an outer fibrous layer and an inner cellular layer)
Cartilage is avascular so is supplied by diffusion from perichondrium

Question 22

What is hyaline cartilage and where is it found?

Answer 22

Most common but the weakest form of cartilage

Found in articular surface of joints, costal cartilages and epiphyseal growth plates

Question 23

What are the properties of hyaline cartilage?

Answer 23

Type II collagen fibres (short and dispersed) 
Proteoglycans (lots!) 
Perichondrium layer (except on articular surfaces)

Question 24

What is fibrocartilage and where is it found?

Answer 24

Strongest form of cartilage
Found in insertion points of ligaments/ tendons to bone; intervertebral disks; joint capsules; knee menisci; pubic symphysis; temporomandibular joint

Question 25

What are the properties of fibrocartilage?

Answer 25

``` Type I collagen (thick parallel bundles alternating with hyaline matrix) No perichondrium (however often found next to hyaline cartilage) ```

Question 26

How can joints be classified?

Answer 26

Synarthrodial (fixed, no movement) Amphiarthrodial (slight movement) Diarthrodial (free movement)

Question 27

What are fibrous joints?

Answer 27

Bones connected by dense connective tissue | No cartilage present

Question 28

Where are fibrous joints found?

Answer 28

Sutures of skull (synarthrodial) | Syndesmoses - interosseous membrane connecting long bones (amphiarthrodial)

Question 29

What are cartilaginous joints?

Answer 29

Bones connected entirely by cartilage (hyaline, fibrocartilage or both) Allow for more movement than fibrous joint but less than others e.g. synovial Primary and Secondary

Question 30

What are primary cartilaginous joints?

Answer 30

Only hyaline cartilage present | [e.g. epiphyseal growth plate, costal cartilages)

Question 31

What are secondary cartilaginous joints?

Answer 31

Hyaline cartilage lines bone with pad of fibrocartilage in between the hyaline [e.g. intervertebral discs, pubic symphysis, manubriosternal joint]

Question 32

What are the features of synovial joints?

Answer 32

Joint cavity between bones containing synovial fluid Hyaline cartilage lines bones Joint enclosed in a joint capsule (which has an outer fibrous membrane and an inner synovial membrane which secrets synovial fluid) Fibroelastic ligaments cross joints to prevent excessive movement and provide reinforcement

Question 33

What is a bursa?

Answer 33

Sac made of synovial membrane and containing synovial fluid | Reduces friction between structures

Question 34

What are the various types of synovial joints?

Answer 34

Classified by movement: Hinge (flexion/ extension) Ball and socket (movement in several axes) Plane (gliding/ sliding) Saddle (concave and convex surfaces) Pivot (rotation) Condyloid (flexion/ extension/ adduction/ abduction, circumduction)

Question 35

What are the risk factors for osteoarthritis?

Answer 35

``` Genetics Age Female Trauma Mechanical stress (on joints) Obesity High bone density Low bone density (increases risk of progression to hips and knees) ```

Question 36

What is the difference between primary and secondary osteoarthritis?

Answer 36

``` Primary = caused by genetic factors and occurs in the absence of a precipitating insult Secondary = caused by sequelae of joint pathology (trauma, infection, inflammation etc.) ```

Question 37

What is the pathophysiology of osteoarthritis?

Answer 37

1. Changes in composition of cartilage (reducing shock absorption) 2. Erosion of cartilage in joints causing fissures 3. Ulceration of cartilage (exposes underlying bone causing microfractures and subchondral cysts) 4. New bone growth (osteophytes, subchondral sclerosis) 5. Synovitis 6. Thickening of joint capsule (causing stiffness and reduced movement)

Question 38

What radiographic changes can be seen in osteoarthritis?

Answer 38

Joint space narrowing (loss of cartilage) Subchondral cysts and sclerosis Osteophytes (hard swellings around small hand joints) Malalignment

Question 39

What are Herbeden Nodes?

Answer 39

Hard swellings around distal interphalangeal joints

Question 40

What are Bouchards Nodes?

Answer 40

Hard swellings around proximal interphalangeal joints

Question 41

What are the signs and symptoms of osteoarthritis?

Answer 41

``` Joint stiffness and pain (worse on movement) Functional limitation (restricted movement) Rest/ night pain Crepitus Bony swelling Joint effusion Joint instability/ deformity Muscle wasting ```

Question 42

What is the management for osteoarthritis?

Answer 42

Education Non-pharmacological (exercise/ physio/ aids) Pharmacological pain management (topical/ oral) Surgical (joint replacement, fusion or excision/ realignment surgery)

Question 43

What are the forms of inflammatory arthritis?

Answer 43

Rheumatoid arthritis Spondyloarthritis (e.g. psioratic, ankylosing spondylitis, enteropathic e.g. IBD) Crystal arthritis (e.g. gout)

Question 44

What is rheumatoid arthritis?

Answer 44

Multi-system autoimmune inflammatory disorder, primarily affecting the joints Symptoms caused by inflammation of synovial membrane and articular surfaces leading to joint destruction Characteristics include warm, tender and swollen joints; morning stiffness (lasts approx. 1 hour) and joint deformities

Question 45

What characterises investigation findings for rheumatoid arthritis?

Answer 45

positive Rheumatoid factor | Raised inflammatory markers

Question 46

What causes gout?

Answer 46

Inflammatory response to urate crystals deposited in and around the joint and synovial fluid leading to synovitis, cartilage destruction and joint degeneration Caused by hyperuricaemia (high levels of uric acid) leading to crystal formation typically in peripheries due to lower temperatures (e.g. metatarsal-phalangeal joints)

Question 47

What is secondary gout?

Answer 47

5% of cases Factors causing overproduction or underexcretion of uric acid e.g. alcohol, drugs, chronic renal failure, high purine diet

Question 48

What is primary gout?

Answer 48

95% of cases | Inherited disorder causing overproduction or underexcretion of uric acid

Question 49

What are the signs and symptoms of acute gout?

Answer 49

Sudden onset Joint inflammation (tender, swollen, hot, red) - typically first metatarsophalangeal joint Can be precipitated by excess food or alcohol, dehydration or diuretics

Question 50

What are the signs and symptoms of chronic (tophaceous gout)?

Answer 50

Tophi (deposits of monosodium urate crystals in bursae, tendons, cartilage or periarticular bones) Chronic joint pain Associated with renal impairment and long-term use of diuretics

Question 51

What are the radiographic changes seen in gout?

Answer 51

``` Joint effusion Bony erosions 'punched out' Opacities (tophi) in soft tissue Soft tissue swellings Narrowing of joint spaces (in later stages) ```

Question 52

How can gout be managed?

Answer 52

Lifestyle changes (e.g. reduce alcohol; avoid purine-rich food such as red meat, shellfish and spinach; weight loss; medication review esp. diuretics) NSAIDs or Colchicine for acute attacks Allopurinol (a Xanthine Oxidase Inhibitor) to reduce uric acid synthesis in chronic gout