MSK - Bones And Joints

Question 1

How many bones are there in the body?

Answer 1

206

Question 2

What are the main functions of the skeleton?

Answer 2

• support
• protection
• movement
• mineral and growth factor storage
• haematopoeisis

Question 3

What are the different classifications of bone by shape?

Answer 3

• flat bone (eg frontal part of skull)
• sutural bone
• irregular bone (eg vertebra)
• long bone (eg femur)
• sesamoid bone (eg patella)
• short bone (eg carpal)

Question 4

What is the function of a sesamoid bone?

Answer 4

• modify pressure
• diminish friction
• alter direction of pull of a tendon

Question 5

What is the main shaft of a long bone called?

Answer 5

Diaphysis

Question 6

What is the ‘neck’ of a long bone called?

Answer 6

Metaphysis

Question 7

Describe the composition of short, flat and sesamoid bones

Answer 7

• consist mainly of spongy bone
• thin layer of periosteum covered compact bone on outside
• no epiphysis or diaphysis
• contain bone marrow between trabeculae

Question 8

What supplies the blood to bone marrow?

Answer 8

Nutrient artery - enters diaphysis via nutrient foramen

Question 9

What supplies blood to the periosteum and outer third of the cortex?

Answer 9

Periosteal arteries

Question 10

What supplies blood to the epiphysis of a long bone?

Answer 10

Epiphyseal artery

Question 11

What is avascular necrosis?

Answer 11

Death of bone due to interruption of blood supply. Leads to collapse of necrotic segment and secondary osteoarthritis
(Also known as osteonecrosis, aseptic necrosis, ischaemic necrosis)

Question 12

What are the causes of avascular necrosis?

Answer 12

• fracture
• dislocation
• steroid use
• radiation
• decompression sickness (the bends)

Question 13

What is a joint?

Answer 13

Articulation between two or more bones

Question 14

What are the three structural classifications of joints?

Answer 14

• fibrous
• cartilaginous
• synovial

Question 15

Give some examples of fibrous joints

Answer 15

• sutures of skull

- joints between roots of teeth and bone of mandible/maxilla

Question 16

What is the difference between a primary and secondary cartilaginous joint?

Answer 16

Primary is united by hyaline cartilage, eg. 1st sternocostal joint.
Secondary comprises articulating bones covered with hyaline cartilage, with a pad of fibrocartilage between them, eg. intervertebral disc, manubriosternal joint

Question 17

Give some characteristics of synovial joints

Answer 17

• ARTICULAR CARTILAGE (hyaline cartilage allows smooth, low friction movement and resists compression)
• FIBROUS CAPSULE (contains collagen, completely encloses joint except synovial protrusions, stabilises joint)
• SYNOVIAL MEMBRANE (thin and highly vascularised, lines capsule but does not cover articular cartilage, produces synovial fluid)
• SYNOVIAL FLUID
• INTRA-ARTICULAR MENISCI
• FAT PADS

Question 18

What is a bursa?

Answer 18

A sac lined with synovial membrane and filled with synovial fluid. It can be communicating or non-communicating with the joint cavity

Question 19

What is a tendon sheath?

Answer 19

An elongated bursa which wraps around a tendon to reduce friction

Question 20

What is the function of synovial fluid?

Answer 20

Reduces friction, shock absorption, nutrient and waste transportation

Question 21

What is the composition of synovial fluid?

Answer 21

Hyaluronic acid, lubricin, proteinase, collagenase

Question 22

How is blood supplied to synovial joints?

Answer 22

Via periarticular arterial plexus

Question 23

What are the differences in blood supply within the synovial joint?

Answer 23

• articular cartilage is avascular
• fibrous capsule and ligaments have poor blood supply
• synovial membrane has rich blood supply

Question 24

What does Hilton’s law suggest about nerve supply of joints?

Answer 24

Nerves supplying the joint capsule also supply the muscles moving the joint and the skin overlying the insertions of these muscles

Question 25

Describe a planar joint

Answer 25

- articulating surface is flat or slightly curved - gliding/sliding movements - non-axial Eg. Sternoclavicular joint, intercarpal joints

Question 26

Describe a hinge joint

Answer 26

- uniaxial - convex surface of one bone fits into concave surface of another Eg. Knee, ankle, humeroulnar joint of elbow

Question 27

Describe a pivot joint

Answer 27

- uniaxial - rounded/pointed surface of one bone articulates within ring formed by the concavity of another bone and fibrous ligament Eg. Proximal radioulnar joint

Question 28

Describe a condyloid joint

Answer 28

- biaxial - oval shaped condyle of one bone rests on elliptical cavity of another - movements are flexion, extension, abduction, adduction, circumduction Eg. Metacarpophalangeal joints

Question 29

Describe a saddle joint

Answer 29

- biaxial joint - one bone is saddle shaped, other bone fits on top - movements include flexion, extension, adduction, abduction, circumduction Eg. 1st metacarpal joint

Question 30

Describe ball and socket joints

Answer 30

- multiaxial - ball-like surface of one bone fits into cup-like surface of another - movements are flexion, extension, abduction, adduction, circumduction and rotation Eg. Hip, shoulder

Question 31

Give some factors affecting stability and range of motion at synovial joints

Answer 31

- structure/shape of articulating bones - strength and tension of joint ligaments - arrangement and tone of muscles - apposition of neighbouring soft tissues - hormones - use/disuse

Question 32

What is the theory behind joint cracking?

Answer 32

- bones are pulled away from each other - synovial cavity expands - synovial fluid volume stays constant - partial vacuum produced - gases dissolved in synovial fluid and pulled out of solution - makes a popping sound

Question 33

What is the effect of ageing on joints?

Answer 33

- decreased production of synovial fluid - thinning of articular cartilage - shortening of ligaments and decreased flexibility - degenerative changes

Question 34

What are the external signs of arthritis?

Answer 34

redness, swelling, deformity, tenderness, reduced range of movement, abnormal gait

Question 35

What is the most common form of arthritis?

Answer 35

Osteoarthritis

Question 36

What is rheumatoid arthritis?

Answer 36

An autoimmune disorder where antibodies attack the synovium leading to synovial inflammation (pannus)

Question 37

Which other organs are damaged by rheumatoid arthritis?

Answer 37

Eyes, skin, lungs, heart and blood vessels, kidneys, blood

Question 38

What are the X-ray features of rheumatoid arthritis?

Answer 38

- narrowing of joint space - periarticular osteopenia - juxta-articular bony erosions - subluxation and gross deformity