Normal Joint Biology- Ayers

Question 1

What are the 3 types of Normal Joints?

Answer 1

1. Synarthrodial
   - Non-moveable (skull suture)
2. Amphiarthrodial
   - Limited mobility like the SI joint
3. Diarthrodial
   - Most common form
   - Wide range of mobility

Question 2

Describe a Diarthrodial Joint

Answer 2

• Most common joint
• Wide range of mobility
• Bones connected by Joint capsule
• Hyaline Cartilage covers the articulating surface (exceptions are TMJ and SC joints with fibrocartilage.)
• Synovial membrane and Synovial fluid smoothens the movement and provides nourishment.

Question 3

Name the 6 types of Synovial Joints

Answer 3

BPHCGS

Ball and Socket
Pivot
Hinge
Condyloid
Gliding
Saddle

Question 4

Describe the Ball and Socket Joint trade off

Answer 4

Shoulder Joint:

• High range of motion
• However, poor stability. Has Functional stability.
• Shallow Glenoid

Hip Joint:

• High stability
• Deep Acetabulum
• Limited range of motion

Question 5

Describe the Condyloid Joint

Answer 5

2 bones in ellipse

• One Concave
• The other Convex

Question 6

Describe the Pivot Joint

Answer 6

2 Bone

-One bone rotates about the other.

Question 7

Describe the Saddle Joint

Answer 7

• Basal Joint
• Between Trapezium and 1st Metacarpal.

Clinical: Very common site of OA, esp. in Post-menopausal women.

Question 8

2 structural features of Hyaline Cartilage

Answer 8

• Ideal Shock absorber

- Wear resistant

Question 9

Describe Articular Cartilage structurally

Answer 9

Contains NO:

• Blood vessels
• Nerves
• Or Lymphatics
• Nourished by Synovial fluid
• Contain few Chondrocytes (arranged in layers)

Question 10

Describe Articular Cartilage metabolically

Answer 10

• Metabolically active

- Constantly synthesizing Type II Collagen and Proteoglycans

Question 11

What are Proteoglycans?

Answer 11

• Glycosylated Proteins
• With a Hyaluronic Acid Backbone

-With Glycosaminoglycan side chains attached to HA at tight angles.

Question 12

What are the 3 components of Glycosaminoglycans?

Answer 12

1. Chondroitin 6-Sulfate
2. Chondroitin 4- Sulfate
3. Keratin Sulfate

Question 13

Describe the Glycosaminoglycan side chains electrostatically

Answer 13

• GAGs have negatively charged side chains
• H2O is attracted to the charged side chains and thus keeps them separated.
• Lattice is thus well hydrated

Note: This allows Cartilage to be WELL Hydrated.

Question 14

Describe Cartilage Under Compression with respect to water

Answer 14

• Under compressive force, water is expelled from the matrix.
• This allows Cartilage to maximize its elasticity and sustain trauma of normal life effectively.

Question 15

Describe the factors of Joint stability

Answer 15

Stability offered by:

• Fibrous Capsule
• Menisci (some cases)
• Ligament
• Muscular Contraction
• Synovial Fluid

Question 16

What is Synovial Membrane?

Answer 16

Derived from Mesenchymal Cells.

Comprised of 2 Cell types:

Phagocytic Cells:
-Like macrophages; activated by degraded matrix.

Secretory Cells:
-Secrete synovial fluid.

Question 17

What is Synovial Fluid? Describe the normal constituents and their respective amounts

Answer 17

• Secreted by Secretory cells in the Synovial membrane
• Provides lubricant for synovial joint

Normal:

• Clear/Straw colored
• Rich in PGs (viscous fluid)
• Less than 200 WBC/mm3

Inflamed:

• Cloudy
• Less Viscous (string test)
• Less PGs
• Thousands of WBC/mm3

Question 18

Describe the Total Knee Replacement benefit

Answer 18

-Provides a very high functional outcome in patients with osteoarthritis.