Limbs, joints and bone

Question 1

Wolff’s Law

Answer 1

Bone is remodelled according to the forces which are placed upon it.

Question 2

Avascular Necrosis

Answer 2

Cellular death of bone compartments due to interruption of blood supply. Bone structure then collapses.
Leads to pain, loss of joint function and long-term joint damage.

Question 3

Structure of bone

Answer 3

Cortical and trabecular bone
Osteon: An osteocyte cyte which encloses a blood vessel.
Osteocyte: Enclosed within bone, communication via projections and gap junctions. Instruct remodelling through information about the stresses placed on the bone.
Osteoblasts: External to bone. Progenitor for osteocytes. Lay down a matrix and become trapped, they are then osteocytes.
Osteoclasts: Large and external to the bone. Derived from monocytes/macrophages.
- Circumferential/concentric/interstitial lamellae
- Canals containing arteries and veins: Central ( vertical) and perforating (horizontal)
- Perforating fibres (from the periosteum)
- Medullar cavity

Question 4

Hyaline cartilage structure and function

Answer 4

Found on articulating surfaces, ‘glassy’ so allows gliding. Collagen type II. Weakest of all 3 cartilages

Question 5

Types of cartilage

Answer 5

Hyaline, fibrocartilage and elastic cartilage

Question 6

Osteoarthritis

Answer 6

The break down of hyaline cartilage caused by inflammation. Hyaline debris seen. Causes damage to the bone.

Question 7

Radiological features of OA: LOSS

Answer 7

Loss of joint space
Osteophytes
Subchondral cysts
Subchondral sclerosis 
*Chondrocytes maintain cartilage*

Question 8

Ligaments

Answer 8

Formed from bundles of collagen fibres.
Similar to tendons in structure however collagen fibres are in a range of directions - as they must resist the separation of bones in multiple directions.
→ Bone to bone

Question 9

Tendons

Answer 9

Formed from bundles of collagen fibres.
Avascular. Formed from dense irregular connective tissue (type I collagen), also collagen II, elastin, glycoproteins and proteoglycans.
→ Bone to muscle/structures

Question 10

Types of joint

Answer 10

Fibrous
Cartilaginous
(Synovial)

Question 11

Types of synovial joint: Ball and socket

Answer 11

Example:

Planes of movement:

Question 12

Types of synovial joint: Hinge

Answer 12

Example:

Planes of movement:

Question 13

Types of synovial joint: Saddle

Answer 13

Example:

Planes of movement:

Question 14

Types of synovial joint: Plane

Answer 14

Example:

Planes of movement:

Question 15

Types of synovial joint: Pivot

Answer 15

Example:

Planes of movement:

Question 16

Types of synovial joint: Condyloid

Answer 16

Example:

Planes of movement:

Question 17

Fibrous joint: Example

Answer 17

Skull

Question 18

Cartilaginous joint: Example

Answer 18

?

Question 19

Osteoarthritis

Answer 19

Caused by the breakdown of hyaline cartilage, protects the bones of joints.
Chondrocytes, within the cartilage, release proinflammatory cytokines, promoting the breakdown of the cartilage.
Eventually the cartilage is broken down and bone-bone contact is seen (DETRIMENTAL).
Debris of cartilage adds to this breakdown, as it creates friction.
Symptoms: Joint pain, stiffness, swelling,

Question 20

Fibrocartilage: Function

Answer 20

• Articular discs within joints: E.g. menisci within the knee. A fibrocartilaginous ring which deepens the socket.
• Can also act to add tensile strength (resists and distributes highly compressive forces)
• Can be found in synovial joints. No perichondrium (connective tissue which envelopes cartilage when it is not at a joint)

Question 21

Fibrocartilage: Structure

Answer 21

Dense.
Alternating layers of hyaline cartilage matrix and thick layers of dense collagen fibres, orientated in the direction of functional stress.

Question 22

Tendonitis

Answer 22

Repeated exposure to excessive loads leads to cycles of injury, inflammation and repair, resulting in pain and swelling.
Histopathology: Disorganised collagen, fibres, areas of cell death and increased fibroblast reaction

Question 23

Components of Synovial fluid and subsequent properties

Answer 23

GAG/hyaluronic acid: Increases viscosity
Lubrican: Provides lubrication
Macrophages
Collagenases

Question 24

Functions of the Synovial Fluid

Answer 24

P - Phagocytosis
L  - Lubrication
A - Antimicrobial
N - Nutrition 
T - Transportation 
S - Shock absorption

Question 25

Acute inflammatory arthritis/Synovitis

- Symptoms

Answer 25

The synovial membrane (secretes synovial fluid) can become inflamed during autoimmunity and infection.
This is known as synovitis. This causes the composition of the synovial fluid to change.
Symptoms: Fever, chills. headache, loss of appetite, muscle stiffness.
- 5 cardinal signs of inflammation

Question 26

Articular structures

Answer 26

Tough fibrous capsule, intra-articular structures

Question 27

Periarticular structures

Answer 27

Extra-articular ligaments, tendons and muscles surrounding the joints

Question 28

Bursae

Answer 28

Thin, double membrane (synovial - comes out of the capsule, continuous), synovial filled sacs.
Found near joints and reduce frictional forces between bones and surrounding tissues.

Question 29

Bursitis

Answer 29

Inflammation/irritation of the bursae