Knee Positioning

Question 1

What IR is used for knee views?

Answer 1

10x12

Question 2

What SID is used for knee views?

Answer 2

40”

Question 3

What are the structures seen for an AP knee?

Answer 3

• AP of knee joint including proximal tib-fib articulation
• Symmetric femoral condyles and tibial intercondylar eminence is centered
• Patella completely superimposed on the femur
• Open femorotibial joint space
• Include distal femur and proximal tib-fib

Question 4

How is the patient positioned for an AP knee?

Answer 4

Patient supine with femoral condyles parallel to IR

Question 5

How do you find the tube angle for an AP knee?

Answer 5

By measuring the pelvis thickness through the ASIS

Question 6

What are the tube angles when determining from pelvis thickness?

Answer 6

• <19 cm: 3-5 degrees caudal
• 19-24 cm: 0 degrees
• > 24 cm: 3-5 degrees cephalic

Question 7

Where is the CR for an AP knee?

Answer 7

Centered to knee 1/2” distal to apex of patella

Question 8

How many degrees is the CR angled for an AP knee?

Answer 8

Determined by ASIS measurement

Question 9

What are the structures seen for a 45-degree medial oblique knee?

Answer 9

• Tibia and fibula separated ar their proximal articulation
• Lateral femoral & tibial condyles
• Both tibial plateaus
• Open knee joint
• Margin of the patella projecting slightly beyond the medial side of the femoral condyle
• Include distal femur & proximal tib-fib

Question 10

How is the patient positioned for a 45-degree medial oblique knee?

Answer 10

• Patient supine with ankle supported
• Medially rotate the entire lower limb 45-degrees
• Elevate the hip

Question 11

Where is the CR for a 45-degree medial oblique knee?

Answer 11

Centered to knee 1/2” distal to apex of patella

Question 12

How many degrees is the CR angled for a 45-degree medial oblique knee?

Answer 12

Angle depends on ASIS meaurement

Question 13

What are the structures seen for a 45-degree lateral oblique knee?

Answer 13

• Medial femoral and tibial condyles seen
• Fibula superimposed over the lateral half of the tibia
• Open knee joint
• Both tibial plateaus seen
• Margin of the patella projecting slightly beyond the lateral side of the femoral condyle
• Include distal femur and proximal tib-fib

Question 14

How is the patient positioned for a 45-degree lateral oblique knee?

Answer 14

• Patient supine with ankle supported
• Laterally rotate the entire lower limb 45-degrees
• Elevate the hip

Question 15

Where is the CR for a 45-degree lateral oblique knee?

Answer 15

Centered to knee 1/2” distal to apex of patella

Question 16

How many degrees is the CR angled for a 45-degree lateral oblique knee?

Answer 16

Angle depends on ASIS measurement

Question 17

What are the structures seen for a mediolateral knee?

Answer 17

• Femoral condyles superimposed
• Open joint space between femoral condyles and tibia
• Patella in profile
• Open patellofemoral joint
• Fibular head and tibia slightly superimposed
• Include distal femur and proximal tib-fib

Question 18

Where is the CR for a mediolateral knee?

Answer 18

1” distal to medial epicondyle

Question 19

How is the patient positioned for a mediolateral knee?

Answer 19

• From supine position, patient is rolled up onto affected side
• Place unaffected leg behind or in front of the affected knee
• Femoral condyles perpendicular to IR
• Knee flexed 20-30 degree

Question 20

How many degrees is the CR angled for a mediolateral knee?

Answer 20

5-7 degrees cephalic