Rational imaging of the painful knee

Question 1

Benefits of plain radiography

Answer 1

• `High bone definition
• Good delineation of calcific structures
• Shows fracture patterns / loose bodies
• Best method to assess primary bone tumours
• Quick, cheap and low radiation dose
• Primary test for the majority of knee pathology

Question 2

Limitations of plain radiography

Answer 2

• Poor soft tissue definition
• Early changes are often occult
• 2D representation of 3D structures

Question 3

Benefits of MRI

Answer 3

• Extremely good soft tissue definition, including marrow and cartilage
• Enables better assessment of anatomical location and extension – allowing
better planning for biopsy, chemo/radio and surgery
• Assesses for further/occult lesions
• No radiation

Question 4

Limitations of MRI

Answer 4

• Slow, expensive and claustrophobic
• Can over-estimate severity of benign lesions
• Not everyone can have an MRI

Question 5

What is osteoarthritis (lay definition)

Answer 5

chronic condition characterised by deterioration of cartilage in the
joints, resulting in stiffness, pain and loss of function

Question 6

What is osteoarthritis (medical definition)

Answer 6

Degenerative condition with progressive loss of joint hyaline
cartilage and subsequent injury to the underlying bone

Question 7

What does osteoarthritis result in

Answer 7

• Loss of Joint Space
• Osteophytes
• Subchondral Sclerosis
• Subchondral Cysts

Question 8

When checking for joint space what radiographs are taken and why

Answer 8

Transverse - To check for patella joint loss

Standing and Supine - may be lost while standing

Question 9

What is osteophyte formation?

Answer 9

• this is new bone formation that is trying to protect itself from the increased stress

Question 10

What is Subchondral Sclerosis

Answer 10

This is the bone underneath the cartilage which has got more dense, so more white.

Question 11

What is Subchondral Cysts

Answer 11

a large area of decreased density

Like a bubble in the bone

Question 12

What is rheumatoid arthritis?

Answer 12

A chronic autoimmune inflammatory disease affects the synovium / joints, but onset can be insidious

Question 13

What causes rheumatoid arthritis

Answer 13

Accumulation of CD4 T- cells in the synovium starts a cascade of
inflammatory responses
Thickened, hyperplastic synovial “pannus” forms and subsequent
inflammatory cascade leads to bone/cartilage erosion