Cartilage

Question 1

What is the functions of the menisci?

Answer 1

1. distribute load
2. stabilise the joint
3. shock absorption
4. lubrication
5. proprioception

Question 2

Describe the gross structure of the menisci

Answer 2

1. wedge-shaped cross section (increases contact area between tibia and femur)
2. horns of the menisci attached to the tibia
3. outer rim of the medial meniscus is attached to the joint capsule (less mobile=more likely to injure)
4. posterior horn of lateral meniscus is attached to the femur via the meniscofemoral ligaments
5. lateral meniscus covers relatively more of its tibial plateau (>75% vs 50-75%)

Question 3

Describe the histology of the menisci.

Answer 3

1. comprised of ~70% water, ~25% collagen type 1 and 1-2% proteoglycans
2. mature cells are fibroblasts & chondrocytes
3. PG concentration is greater in inner ⅔ (attract and bind water to assist lubrication)
4. inner zone collagen arrangement is radial (resists compressive forces)
5. outer zone collagen arrangement is circumferential (resists tensile forces)
6. outer ⅓ is vascularised (better healing capacity)
7. outer ⅓ is innervated and contains mechanoreceptors in the horns (proprioception)

Question 4

Describe some mechanical properties of the menisci.

Answer 4

1. high tensile modulus
2. during knee flexion the menisci translate posteriorly relative to the tibia (to maintain contact area and reduce stress)

Question 5

Describe 4 ways the behaviour of fibrocartilage differs from hyaline.

Answer 5

1. fibrocartilage has a higher tensile modulus and higher tensile ultimate stress
2. hyaline has a higher compressive modulus and higher compressive ultimate stress
3. hyaline has a higher shear modulus
4. fibrocartilage has a higher shear ultimate stress

Question 5

Describe 4 ways the behaviour of fibrocartilage differs from hyaline.

Answer 5

1. fibrocartilage has a higher tensile modulus and higher tensile ultimate stress
2. hyaline has a higher compressive modulus and higher compressive ultimate stress
3. hyaline has a higher shear modulus
4. fibrocartilage has a higher shear ultimate stress