Bones and joints

Question 1

What is a joint?

Answer 1

Point of contact between neighbouring bones, cartilage and bones or between teeth and bones.

Question 2

How are joints classified and what are the 3 different types?

Answer 2

Classified according to: i) presence/absence of synovial cavity, ii) type of tissue that binds the bones together.

1. fibrous joints
2. cartilaginous joints
3. synovial joints

Question 3

What are the characteristics of fibrous joints?

Answer 3

• Lack a synovial cavity.
• Articulating bones held very closely together by fibrous CT.
• Permit little or no movement.

Question 4

Give examples of fibrous joints.

Answer 4

• sutures of skull
• inferior tibiofibular joint
• radioulnar interosseus membrane
• posterior sacroiliac joint
• joints between roots of teeth and bone of mandible or maxilla

Question 5

What are the characteristics of cartilaginous joints?

Answer 5

• Lack a synovial cavity.
• Artilculating bones tightly connected by cartilage.
• Permit little or no movement.

Question 6

What are the 2 types of cartilaginous joints? Give examples.

Answer 6

Primary cartilaginous joints

• connective tissue is hyaline cartilage
• e.g. epiphyseal plates

Secondary cartilaginous joints (symphyses)

• connective tissue is a fibrocartilage disc
• e.g. pubic symphysis

Question 7

What are the characteristics of synovial joints?

Answer 7

i) synovial cavity
ii) articular cartilage
iii) articular capsule composed of 2 layers: outer fibrous capsule that may have ligaments and inner synovial membrane which secretes the lubricating synovial fluid that fills the synovial cavity
iv) rich blood and nerve supply
v) many synovial joints also contain:
- accessory ligaments, inc. extracapsular and intracapsular ligaments
- articular discs or menisci

Question 8

Name 2 structures that can reduce friction at some synovial joints during movement.

Answer 8

1. fluid-filled sacs - bursae

2. tube-like bursae - tendon sheaths

Question 9

Name the 6 different types of synovial joints.

Answer 9

1. planar joint
2. hinge joint
3. pivot joint
4. condyloid/ellipsoidal joint
5. saddle joint
6. ball and socket joint

Question 10

Describe and give an example of a planar joint.

Answer 10

• articulating surfaces usually flat or slightly curved
• non-axial joint - only gliding side-to-side or back-and-forth movements
• e.g. sternoclavicular joint

Question 11

Describe and give an example of a hinge joint.

Answer 11

• monoaxial joint at which convex surface of 1 bone fits into concave surface of another bone
• allows flexion and extension
• e.g. knee joint, elbow joint or ankle joint

Question 12

Describe and give an example of a pivot joint.

Answer 12

• monoaxial joint at which rounded/pointed surface of 1 bone articulates with a ring formed partly by another bone and partly by a ligament
• rotation may occur
• e.g. rotation of atlas around dens of axis when turning head

Question 13

Describe and give an example of a condyloid/ellipsoidal joint.

Answer 13

• biaxial joint at which oval-shaped condyl of 1 joint rests against elliptical cavity or another bone
• 4 angular movements (and circumduction) may occur
• e.g. wrist joint

Question 14

Describe and give an example of a saddle joint.

Answer 14

• biaxial joint at which articular surface of 1 bone is saddle-shaped and articular surface of the other bone resembles the legs of a rider sitting the saddle
• is technically a modified ellipsoidal joint in which movement is less restricted
• e.g. joint between trapezium and 1st metacarpal base

Question 15

Describe and give an example of a ball-and-socket joint.

Answer 15

• multiaxial joint at which the ball-like surface of 1 bone rests against the cup-like depression of another bone
• 4 angular movements and rotation may occur
• e.g. shoulder join and hip joint (only examples)

Question 16

What is a gliding movement (at a synovial joint)?

Answer 16

articulating surfaces slide against each other

Question 17

What are the angular movements at synovial joints?

Answer 17

Change in the angle between articulating bones:

• flexion
• extension
• abduction
• adduction
• circumduction (distal end of a bone moves in a circle whilst the proximal end remains stable - combination of 4 angular movements and rotation)

Question 18

What is rotation at a synovial joint?

Answer 18

bone turns around its own longitudinal axis:

• medial/internal
• lateral/external

Question 19

Name 6 factors affecting contact and range of motion at synovial joints.

Answer 19

1. structure/shape or articulating bones
2. strength and tension (tautness) of the joint ligaments
3. arrangement and tone of muscles around the joint
4. apposition of neighbouring soft tissues
5. effect of hormones
6. joint disuse

Question 20

Give an example of a hormone affecting joint motion.

Answer 20

relaxin relaxes pelvic joint towards the end of pregnancy

Question 21

Give 4 effects of ageing on joints.

Answer 21

1. decreased production of synovial fluid
2. thinning of articular cartilage
3. shortening of ligaments and decreased ligamentous flexibility
4. degenerative changes in load-bearing joints