2/13 Osteoarthritis

Question 1

List the compartments of the diarthroidal joint that these disease affects:

RA

Psoriatic arthritis

Gout, pseudogout, and septic arthritis

Osteoarthritis

Answer 1

RA = synovium

Psoriatic arthritis = synovium + tendon

Gout, pseudogout, and septic arthritis = things external to the joint (urate, Calcium pyrophosphate dehydrate (CPPD), sepsis/bugs)

Osteoarthritis = cartilage (hyaline + fibrous)

Question 2

What is the function of the hyaline/articular cartilage?

Answer 2

shock absorber of diarthroidal joints - handles 90% of load-bearing

Question 3

What are the features of NORMAL hyaline cartilage/articular cartilage?

Answer 3

high H2O content
stiff
chondrocytes + collagen fibers distributed throughout proteoglycan matrix
interstitial fluid pressurization (like a gel-pack or sealed moist sponge)
abundant acid mucopolysaccharide (proteoglycans)

Question 4

Is Osteoarthritis an inflammatory or non-inflammatory disease?

Answer 4

NON-inflammatory

Question 5

What is osteoarthritis? What are other subnames of this disease?

Answer 5

progressive, symmetrical disintegration of hyaline + fibrous cartilage with secondary damage to surrounding structures

aka OA, degenerative joint disease (DJD), wear and tear arthritis

Question 6

What is the difference between primary and secondary osteoarthritis?

Answer 6

Primary (idiopathic): very common; involves hands, spine, hips, knees, 1st MTP , et al

Secondary: precedes inflammatory disease, trauma, or metabolic factor, ie, underlying mechanical or metabolic problem such as excessive Fe in hemochromatosis, RA, ACL tear, avascular necrosis, Piaget’s disease

Question 7

What are the lab + radiologic findings of osteoarthritis?

Answer 7

Lab:
ESR <40, RF titer <1:40, Non-inflammatory synovial fluid

Radiologic:
osteophytes (bone spurs), narrowing joint space, subchondral cysts and sclerosis, misalignment of joints

Question 8

What are the major changes found early osteoarthritis? later?

Answer 8

Early in the disease

• INCREASED water content, causing it to be more pliable, which results in excessive deformation, tearing, and cracking with repeated loading
• *1. Small tangential clefts on surface** – shaggy border
• 2. Deep vertical clefts
  3. Splitting process, “fibrillation”
  4. Clumping, hypercelluarity, and hypertrophy of chondrocytes -**first thing you see*
• Reactive new subchondral bone formation
• Extensive loss of acid mucopolysaccharide from matrix with diminished brilliant red dye fixation
• *Later in the disease (**joints look swollen, feels like bone)
• progressive fibrillation + loss of cartilage, resulting on bone-on-bone pathology
• osteophyte formation & subchondral sclerosis
• modest inflammatory infiltrates in synovium
• ligamentous laxity, resulting in weak periarticular muscles

Question 9

Who is the culprit of osteoarthritis?

Answer 9

chondrocytes

Question 10

How does chondrocytes contribute to osteoarthritis?

Answer 10

Chondrocytes respond to repetitive excess mechanical loading by **promoting matrix degradation **and downregulating processes essential for cartilage repair (counter-productive!!)

proliferate + syntheseize matrix proteins/collagen, MMPs, growth factors, cytokines & other inflammatory mediators

MMPs degrade the matrix, which results in debris products in the synovial space, which further up-regulates these cellular events; ultimately result in a loss of cartilage

Anabolic factors, like BMPs & TGFb cause osteophyte formation, and chondrocyte proliferation and hypertrophy, increased cartilage calcification (tidemark duplication), & microfractures with angiogenesis from subchondral bone.

Question 11

Osteoarthritis affects which joints in the hand the most?

knees?

Answer 11

Hands: greatest incidence in DIP + thumb base (1st carpometacarpal joint space), followed by PIP joint

• *Knees**: greatest incidence medial compartments, but lateral and patella femoral joint is also affected
• both medial affected = bow-legged
• both lateral affected = knocked-knees
• medial + lateral compartment = windswept knees

Question 12

PIP and DIP is also known as….

Answer 12

PIP = Bouchard’s nodes
DIP = Heberden’s nodes

Question 13

What should you think of if you see osteoarthritis in the MCP joints, especially in a young person?

Answer 13

think Hemochromatosis! (not OA)

Question 14

Is OA more common in men or women?

Answer 14

Females:Males = 4:1; likely due to hormonal changes

Question 15

How does obesity contribute to OA?

Answer 15

for every 10 pounds increase in weight, the force on the knee by 30-60 pounds with each step

Question 16

What are the 4 best treatments for OA?

Answer 16

• Weight loss
• Exercise – improves joint stability
• Other non-pharmacologic approaches
• Joint replacement

When all else fails: Total Knee Replacement (TKR)

No medications has been shown to alter OA progression; only OA pain is treated