Joints

Question 1

Functions joints allow:

Answer 1

• permit limited movement
• transfer forces from one bone to another

Question 2

What are the joint classifications? And how are they united?

Answer 2

• fibrous (allow little to no movement, united by fibrous tissue)
• cartilaginous (allows limited movement, united by hyaline or fibrocartilage)
• synovial (allows movement, united by a synovial joint capsule)

Question 3

Joints can be classified by range of motion possible - what are they?

Answer 3

• synarthrosis (no movement)
• Amphiarthrosis (limited mobility)
• Diarthrosis (free movement)

Question 4

Describe the synovial joint

Answer 4

• majority of joints
• bones separated by fluid-filled space, lined with hyaline cartilage (low friction and allows the most movement of all joint types)
• articulating surfaces and joint enclosed by joint capsule
• inner synovial membrane
• strengthened by outer fibrous layer

Question 5

What does the synovial membrane do?

Answer 5

• contains synovial lining cells which produce hyaluronic acid for viscosity
• produced synovial fluid
• inner synovial membrane strengthened by outer fibrous layer
• contains simple squamous epithelium
• contains blood vessels and lymph (fenestrated capillaries, reabsorb and renewal of fluid)

Question 6

What does articular or hyaline cartilage do?

Answer 6

• reduces friction and acts as a shock absorber

Question 7

What does the joint capsule do?

Answer 7

• contains synovial fluid
• an envelop around the joint

Question 8

What does synovial fluid do?

Answer 8

• provides cushioning
• takes nutrients to the site and waste away from the site
• lubricates the joint and reduces friction
• maintains articular contact

Question 9

Describe articular hyaline cartilage

Answer 9

• no blood vessels or nerves
• withstand loads of pressure without pain or bleeding
• slow/limited healing and repair
• good at resisting compression
• smooth surface, low friction

Question 10

Describe the connective tissue in joints

Answer 10

• few cells, chondrocytes 1-3%
• extracellular matrix
• hydrophilic proteoglycans (e.g., hyaluronic acid)
• water 70-80%
• collagen fibres (type 2)

Question 11

Describe ligaments within a joint?

Answer 11

• strong white/fibrous ligaments hold together bones
• restrict movement (along with the shape of articular surfaces)
• intra vs extra capsular

Question 12

Describe intracapsular ligaments

Answer 12

• within joint capsule
• not within joint space
• synovium reflects over them

Question 13

Describe menisci or semilunar cartilages

Answer 13

• found in some synovial joints (stifle, teres major)
• crescent shaped fibrocartilages
  . load distribution
  . shock absorption
  . stabilisation

Question 14

What protects tendons near joints?

Answer 14

• sesamoids ~ ossification or chondrification
• tendon sheaths and bursae ~ sacs/tubes containing cavities filled with synovial fluid and with synovial lining

Question 15

Describe how a joint gets it nervous and vascular supply

Answer 15

• blood vessel to epiphysis and joint capsule (not cartilage)
• free sensory fibres (pain) from joint capsule/synovium
• motor fibres to blood vessels
• sensory fibres from blood vessels
• proprioceptive fibres from joint capsule

Question 16

What are the 6 degrees of freedom?

Answer 16

1. cranial-caudal translation
2. proximal-distal translation
3. medial-lateral translation
4. rotate around the craniocaudal axis
5. rotate around the proximodistal axis
6. rotate around the mediolateral axis

Question 17

what does rotating around the mediolateral axis result in?

Answer 17

• flexion = bending
• extension = straightening

Question 18

What does rotation around craniocaudal axis result in?

Answer 18

• adduction = bringing back towards the midline of the body
• abduction = taking away from the midline from the body

Question 19

rotation around the proximodistal axis will result in what?

Answer 19

• pronation (internal rotation) = lateral surface rotated inwards
• supination (external rotation) = medial surface rotated outwards

Question 20

Movement types are often what?

Answer 20

• coupled
• biological joints don’t strictly do pure movements in just one degree of freedom

Question 21

The mobility of a joint depends on what?

Answer 21

• the shape of the bones
• the ligaments connecting them

Question 22

What are the types of synovial joints

Answer 22

1. plane (prince)
2. hinge (harry)
3. pivot (pulled)
4. condylar (charles)
5. ellipsoid
6. saddle
7. ball-and-socket (bag)

Question 23

Describe a plane joint

Answer 23

• two flat surfaces
• translation, no real rotational movements
• articular process of equine cervical vertebrae

Question 24

Describe the hinge joint

Answer 24

• cylindrical surface and corresponding receiving surface
• usually a notch to limit sideways motion
• movement (rotation) in one plane only
• e.g., equine metacarpophalangeal joint

Question 25

Describe the pivot joint

Answer 25

- peg fitted withing ring - rotational movements of peg within ring - bovine atlantoaxial joint

Question 26

Describe the condylar joint

Answer 26

- two knuckled-shaped condyles with with corresponding concave surfaces - mostly rotation about transverse axis running between condyles, but rotation about other axes and translation also possible

Question 27

Describe a ellipsoidal joint

Answer 27

- ovoid convex surface with corresponding concavity - rotation and translation in two planes

Question 28

Describe the saddle joint

Answer 28

- two fitting surfaces, each maximally convex in one direction and maximally concave in another - rotation and translation dictated by geometry of surfaces

Question 29

Describe a ball and socket joint

Answer 29

- sphere and cup morphology - up to six degrees of freedom