Joint Pathology

Question 1

What are the normal features of the synovial membrane?

Answer 1

Lines the internal aspect of the joint capsule of synovial joints
Produces synovial fluid to lubricate joint & nourish cartilage (plasma filtrate + hyaluronic acid)
Not an epithelium - no basement membrane or junctional complexes
Has macrophage and fibroblast like cells
Highly vascular

Question 2

What is osteoathritis?

Answer 2

Chronic degeneration of a few joints - usually weight bearing/heavy use joints or joints previously injured

Question 3

What is the general pathogenesis of osteoathritis?

Answer 3

Damage to cartilage stimulating chondrocyte activity & proliferation
Depletion of water and matrix and released of IL-1, MMPs and collagenases
Loss of normal articular cartilage function
Uneven weight loading to the joint
Shedding and destruction of the cartilage - uneven
Bone on bone rubbing

Question 4

What are the pathological features of oesteoarthritis i.e. those seen histologically or on XRAY?
Why do they occur?

Answer 4

Bone on bone rubbing & uneven weight loading leads to thickening on sub-chondral bone, eburnation, sub-chondral cyst formation and osteophyte development

Damaged & sheding of cartilage seen as fibrillation & erosion

Question 5

What are the risk factors of osteoarthritis?

Answer 5

Increasing age 
Genetics
Previous damage/trauma to joint 
Heavy use of joint 
Obesity 
Most risk factors relate to damage of cartilage

Question 6

Signs of osteoathritis?

Answer 6

No systemic symptoms 
Gradual onset of deep bone pain (achey)
Reduced RoM
Crepitus (grinding)
Osteophytes, subchondral thickening & cysts seen on XRAY

Question 7

What is Rheumatoid arthritis?

Answer 7

Autoimmune, systemic inflammatory disease that causes progressive destruction of the joints

Question 8

What is the general pathophysiology if rheumatoid arthritis?

Answer 8

The inflammatory stimulus and mediators are unknown but thought to be due to:

• Underlying Th1 and Th17 cells and inflammatory cytokines (TNF, IL-6, IL-1)
• Induction of macrophages, fibroblasts, osteoclasts and B cells

Question 9

What is the presentation of rheumatoid arthritis?

Answer 9

Often starts symmetrically in the joints of the hands or feet
Signs of inflammation at joints
Systemic systems - Fever, LOW, anorexia
Rheumatoid nodules
Volar displacement of phalanges and swan neck deformity
Morning stiffness of hands

Question 10

What are the pathological features of rheumatoid arthritis?

i.e. histological & XRAY

Answer 10

Loss of bone & cartilage
Uniform loss of joint space
Fibrosis & calcification that fuses joints 
Osteopenia (next to joint)
Subchondral erosion 

Changes to synvovial membrane - mononuclear infiltrate, germinal centres, hyperplasia and villous formation
Pannus formation (inflammatory granulation tissue) - erodes the cartilage & bone)
Neutrophils & fibrin in the joint space

Question 11

What are risk factors for rheumatoid arthritis?

Answer 11

Genetic
Female
Increasing age (usually between 25 - 55 yo)
Smoking

Question 12

How is RA diagnosed?

Answer 12

Inflammatory markers - CRP, ESR
Rheumatoid factor
Anti-CCO
XRAY findings - juxta-articular osteopenia, symmetrical loss of joint space, subchondral erosions

Question 13

What is Gout?

Answer 13

Acute inflammatory condition effecting joints (usually single unless chronic) due to crystal precipitation of uric acid

Question 14

What causes gout?

Answer 14

Precipitation of uric acid as crystals in the joints due to increased uric acid production in metabolism, decreased excretion or increased in take in diet

Question 15

When does gout manifest?

What goes it to manifest and what is the common first presentation?

Answer 15

Gout is usually asymptomatic for decades despite elevated & rising uric acid levels (hyperuremic)

Precipitation eventually occurs and is often triggered by high alcohol intake, high purine meal or dehydration

Usually presents initially in the big toe (podagra) in the middle of the night - cooler and lower pH which facilitates precipitation

Question 16

What is the mechanism for pain in acute gout?

Answer 16

Crystal formation activates inflammatory cells, synovium and complement
Pain caused by inflammasome activation (IL-1), spillage of phagolysome when neutrophils ingest crystals which cause them to rupture

Question 17

What happens if acute gout goes on untreated?

Answer 17

Progresses to chronic gout where multiple joints may become involved (not a symmetrical distribution)
Commonly crystals precipitate in the ear

Chronic inflammation can lead to pannus formation which damages the joint

Precipitation of uric acid also occurs in the soft tissue (tophi) which stimulate granulomatous inflammation

Question 18

What signs on XRAY result from gout?

Answer 18

There is NO loss of joint space or periarticular osteopenia

Can get punched out erosions and sclerotic edges of the joint

Question 19

Why is uric acid not reliable in gout diagnosis?

Answer 19

High uric acid levels doesn’t mean there is gout (levels can remain high for decades before precipitation occurs)

Levels may not be elevated when acute gout occurring

Question 20

What are some risk factors for gout?

Answer 20

Increasing age
Male
Obesity, hypertension and metabolic syndrome
Genetics, ethnicity
Menopause
Diet - high purine
Conditions which effect metabolism and excretion of uric acid