9. Arthritis 11

Question 1

Where do bones grow from?

Answer 1

Growth plate (epiphyseal plate)

Question 2

State Hueter-Volkmann’s Law?

Answer 2

Increased compression at the growth plate slows down longitudinal growth
Increased tension at the growth plate speeds up longitudinal growth

Question 3

Give an example of where this can be used to correct an abnormality.

Answer 3

Eight Growth Plate – if there is abnormal growth on one side of the distal tibial physis you can inset a metal plate with pins on either side of the growth plate to prevent further growth on that side and allow the other side to catch up

Question 4

What are the three different types of knee alignment?

Answer 4

Normal/Neutral
Varus – bowed legs
Valgus – knocked knees

Question 5

What types of athletes get varus alignment?

Answer 5

Footballers

Question 6

Which part of the knee joint would be loaded most in varus alignment?

Answer 6

The inner part

Question 7

What are the consequences of this?

Answer 7

It will wear out the cartilage and cause osteoarthritis

Question 8

What surgical intervention can be performed before the onset of osteoarthritis to realign the knee joint?

Answer 8

Osteotomy – this involves taking a wedge out of the tibia to realign the knee joint

Question 9

State Wolff’s Law.

Answer 9

Bone in a healthy person will adapt to the loads under which it is placed

Question 10

Give an example that illustrates Wolff’s law.

Answer 10

Surfer’s knots

Question 11

What are the two surfaces of the cortical bone?

Answer 11

Periosteal surface

Endosteal surface

Question 12

Load on the bones causes an increase in cortical thickness – how is this response to loading different in children compared to adults?

Answer 12

Children – have an active periosteum and endosteum so they get increased bone growth at BOTH surfaces
Adults – their periosteum is less active – so the response to increased loading is mainly at the endosteal surface

Question 13

A lot of problems to do with body shape occur in utero. Give an example of such a problem that is associated with 9-10% of cases of osteoarthritis

Answer 13

Developmental Dysplasia of the Hip (DDH)

Question 14

Describe the appearance of the hip joint in someone who had DDH.

Answer 14

The hip joint may be higher than normal
The acetabulum is shallow and it doesn’t cover much of the femoral head
This leads to increased load and wear

Question 15

Why is it important to spot these deformities early?

Answer 15

If these deformities are caught early, they could realign them and cause a remodelling of the joint to allow normal stance

Question 16

Name and describe two abnormalities of the hip joint.

Answer 16

Cam – bump on the neck

Pincer – the acetabulum tries to capture the hip joint so it is much deeper than normal (mainly seen in females)

Question 17

What are the negative consequences of Cam abnormality?

Answer 17

Deep flexion will cause repeated impact between the bump on the femoral neck and the acetabular rim leading to the wearing away of the cartilage –> osteoarthritis

Question 18

What are the negative consequences of Pincer abnormality?

Answer 18

The femoral neck will impact with the deepened acetabular labrum and cause compacting of the femoral head posteriorly (this will cause a contre-coup type erosion of the cartilage on the posterior acetabular surface)

Question 19

Name the two cruciate ligaments of the knee joints and state their roles with regards to sliding at the knee joint.

Answer 19

Anterior cruciate ligament – stops the tibia from sliding forwards
Posterior cruciate ligament – stops the tibia from sliding backwards

Question 20

What is a synovial joint?

Answer 20

A joint covered with hyaline cartilage or fibrocartilage that is surrounded by a fibrous capsule with a synovial membrane on the inside producing synovial fluid to lubricate the joint

Question 21

What is the structural difference between the medial and lateral menisci?

Answer 21

The lateral meniscus has a much tighter C shape

Question 22

What are the two main functions of cartilage?

Answer 22

Shock absorption

Low friction

Question 23

Which type of collagen is found in cartilage?

Answer 23

Type 2

Question 24

Describe the arrangement of collagen in the superficial layer andexplain why they are arranged like this.

Answer 24

Horizontally – resists shear forces

Question 25

Describe the arrangement of collagen in the deep layer and explain why they are arranged like this.

Answer 25

Vertically – resists compressive forces

Question 26

What provides the nutrition to the tissue above the tidemark?

Answer 26

Synovial fluid

Question 27

What is the downside to the lack of blood supply above the tidemark?

Answer 27

This means that if the cartilage superficial to the subchondral bone is damaged, it can’t really heal itself

Question 28

What is the name given to the pattern of fibres that form the collagen network in bone?

Answer 28

Arcades

Question 29

What happens to your tibia when the ACL snaps and what other structures will try to hold it in place?

Answer 29

It slides forwards
The meniscus will try to hold it in place
NOTE: if you don’t repair the ACL you will get meniscal tears because they are being strained in trying to keep the femur in place on the tibial plateau

Question 30

Describe the vascularity of the menisci.

Answer 30

Only the peripheral 1/3 has a blood supply

Question 31

List the layers of articular cartilage (6)?

Answer 31

Superficial gliding zone
Middle transitional zone
Deep radial zone
Tidemark
Calcified cartilage
Subchondral bone