Imaging - Knee and Foot and Ankle

Question 1

What are some routine radiograph views of the knee?

Answer 1

AP
Lateral
PA Axial “Tunnel” View
Tangential View

Question 2

What does the knee AP view show?

Answer 2

Visualizes distal Femur, proximal Tibia and respective joint, and Fibular head

Question 3

What are some important observations of the structures in a knee AP view?

Answer 3

• Patella superimposed and not typically visible unless patella baja
• Well defined joint spaces and equal
• Alignment of Femur and Tibia
• Distinct cortical margins and cancellous markings

Question 4

What does a knee lateral view show?

Answer 4

Visualizes profile of PF joint

Question 5

What are some important observations in a knee lateral view?

Answer 5

Important observations- patellar alta/baja positioning

Question 6

What should we see regarding the length of the patellar tendon and patella?

Answer 6

Length of patella and patellar tendon should be similar, within 20% variance

Question 7

What does the knee PA axial “tunnel” view show?

Answer 7

Intercondylar fossa and eminence
Posterior Femur and Tibia
Tibial plateaus

Question 8

What is the knee PA axial tunnel view used to detect?

Answer 8

Used to detect loose bodies, osteochondral defects, or narrowing of Tibiofemoral joint space

Question 9

Why is the knee PA axial tunnel view often performed?

Answer 9

Often performed in standing for Age-related changes

Question 10

What are some important observations with the knee PA axial tunnel view?

Answer 10

Important observations
Tunnel should be open, round and not squared off
Well defined joint spaces and equal

Question 11

What is the knee tangential view showing?

Answer 11

Visualizes PF joint space and surfaces

Question 12

What should we observe with the knee tangential view?

Answer 12

Smooth and distinct joint surfaces
Sulcus angle
congruence angle

Question 13

What does the sulcus angle tell us?

Answer 13

depth of sulcus; if shallow more prone to dislocations

Question 14

What is the congruence angle?

Answer 14

• Helps to define patellar position within the sulcus
• If > 16° lateral to the zero line, more prone to dislocations

Question 15

What are some routine radiographs of the ankle?

Answer 15

AP
AP Oblique (mortise)
Lateral

Question 16

What does the ankle AP view visualize?

Answer 16

Visualizes distal Tibia and Fibula and Talar dome

Question 17

What are some important observations in the ankle AP view?

Answer 17

• Lateral malleolus more distal than medial
• Visualize upper and medial talus- a medial or lateral shift of Talus is abnormal
• Distal Tibiofibular joint space- an abnormally wide joint is abnormal

Question 18

What is an ankle AP oblique mortise view?

Answer 18

Visualizes entire ankle mortise with 15-20° of hip IR

Question 19

What are some important observations in an ankle AP oblique mortise view?

Answer 19

• Entire talocrural joint space
• Mortise width- typically, 3-4 mm or < ½ a cm all the way around is normal
• Distal Tibiofibular joint- NO optimal radiographic parameter exists to assess syndesmotic integrity but > 6 mm is utilized

Question 20

What does the ankle lateral view visualize?

Answer 20

• Tibiotalar and subtalar joints
• Talonavicular and Calcaneocuboid joints
• Bony members

Question 21

What are ankle stress views?

Answer 21

X-ray while performing ligamentous Special Test

Question 22

What is the ankle anterior drawer stress view measuring?

Answer 22

Measure from posterior Tibia to posterior Talus

Question 23

What is an normal value for the ankle anterior drawer stress view radiograph? abnormal?

Answer 23

Normal = 5 mm or a ½ a cm
Abnormal = > 10 mm or 1 cm
5-10 mm of separation requires comparison between sides

Question 24

What is an ankle EV/IV stress view looking at?

Answer 24

Measure angle between bottom of Tibia and Talar dome

Question 25

What are abnormal findings with the ankle EV/IV stress views?

Answer 25

Mortise widens Talar displacement or tilt * > 15° for IV and > 10° for EV are abnormal * Also, abnormality exists if > 5° difference between sides of the body

Question 26

What are some routine radiographs of the foot?

Answer 26

AP Lateral Oblique

Question 27

What does the foot AP visualize?

Answer 27

Visualizes the mid- and forefoot

Question 28

What are some important observations with the foot AP view?

Answer 28

- Note individual mid- and forefoot bones along with sesamoid bones - 1st intermetatarsal angle= intersection of lines bisecting 1st and 2nd MT shafts (Normal < 5-10°)

Question 29

What is the foot lateral view visualizing?

Answer 29

Subtalar, talonavicular, and calcaneocuboid joints and members

Question 30

How is the foot lateral view different from the lateral ankle view?

Answer 30

Different from lateral ankle view bc less Tibiofibular imaged

Question 31

What is the foot oblique view?

Answer 31

Foot and leg medially rotated ** primarily for forefoot

Question 32

What does the foot oblique view visualize?

Answer 32

- Primarily for forefoot - All tarsals except 1st Cuneiform and a portion of the Talus

Question 33

What are some important observations with the foot oblique view?

Answer 33

- MTs image with sharp clearly defined cortical borders - Sesamoids - 2nd-4th distal phalanges difficult to visualize * Note joint spaces of intermetatarsal and midtarsal joints

Question 34

What is the Bernese Foot and Ankle CDR?

Answer 34

≥ 91% sensitive and specific - Ankle radiographs are required with P! from either of the following: * Compress malleolar fork with palm ~4 inches above fibular tip and avoiding the injured region * Press thumb pad directly on medial malleolus - Foot radiographs are required with P! while stabilizing calcaneus and then compressing midfoot into rearfoot

Question 35

What are the Ottawa food and ankle CDR?

Answer 35

98% sensitive and 88% specific Ankle radiographs are required with: - P! along distal 2.5 inches of posterior border OR tips of fibula OR tibia - Inability to walk 4 steps immediately OR in ER Foot radiographs are required with: - P! at 5th MT base OR Navicular - Inability to walk 4 steps immediately OR in ER

Question 36

What should be the ankle position with Matle’s test? PF or DF?

Answer 36

PF

Question 37

What is an ultrasound?

Answer 37

Ultrasound waves are absorbed, reflected, and diffused differently from varying tissues to construct an image

Question 38

What are the advantages of an ultrasound?

Answer 38

- Offers real time information for superficial soft tissue - Higher resolution for superficial tendon, ligament, and muscle than MRI

Question 39

What are some major disadvantages of an ultrasound?

Answer 39

- Inability to scan deeper joint structures - image quality highly dependent on operator

Question 40

What do higher (brighter) signals come from on US?

Answer 40

Higher (brighter) signal from reflection of smoother and denser structures indicate swelling, tendinosis (fibrosis/degeneration), aka hyperechoic appearance

Question 41

What do irregular borders or lack of structure indicate on US?

Answer 41

tears

Question 42

What does a wider structure indicate on US?

Answer 42

swelling, thickening

Question 43

When should we use a radiograph?

Answer 43

initial images

Question 44

When are CT and MRI recommended?

Answer 44

complex fractures and osteochondral lension

Question 45

When is a MRI recommended?

Answer 45

Stress fx and tendon abnormalities

Question 46

When is a MRI arthrography (with contrast) recommended?

Answer 46

for ligamentous and cartilage issues

Question 47

When is US appropriate?

Answer 47

For superficial soft tissue abnormalities