Tibia, Fibula, and Knee Assessment

If the ankle and knee cannot fit on one IR, what course of action should the radiographer take?

• Take an image to include the joint nearest to the area of injury

• Second collimated-down image of the other joint

• Include at least 2” of overlap

What is the CR for the AP projection of the tibia and fibula?

Perpendicular to the center of the leg

For the AP projection of the tibia and fibula, how should the femoral condyles be positioned?

Parallel to the IR

How should the foot be positioned for the AP projection of the tibia and fibula?

Foot should be dorsiflexed and in a vertical position

According to Merrill’s, how much collimation should you have beyond the ankle and knee?

1 1/2” (at least 1”)

How should the proximal and distal articulations of the tibia and fibula appear on a properly positioned AP projection of the tibia and fibula?

Moderately overlapped

How should the midshaft of the fibula appear with respect to the tibia in a properly positioned AP projection of the tibia and fibula?

Free of superimposition

For the lateral projection of the tibia and fibula, which side is the patient rotated onto?

Rotated onto the affected side

What is the CR for the lateral projection of the tibia and fibula?

Perpendicular to the midpoint of the leg

What structures MUST be included on the image for a lateral projection of the tibia and fibula?

The tibia, fibula, and adjacent joints

How should the distal fibula be demonstrated with respect to the tibia in a properly positioned lateral projection of the tibia and fibula?

Distal fibula superimposed by the posterior half of the tibia

How should the tibia and fibula appear on the proximal end in a properly positioned lateral projection of the tibia and fibula?

Slight overlap of the tibia on the proximal fibular head

How should the tibial and fibular bodies appear with respect to each other in a properly positioned lateral projection of the tibia and fibula?

With moderate separation (except at articular ends)

For the lateral projection of the tibia and fibula, divergent beam could cause the femoral condyles NOT to be superimposed in which direction?

Superiorly and inferiorly

For the lateral projection of the tibia and fibula, to indicate no rotation, which surface of the femoral condyles should be superimposed?

Anterior surface

For the AP projection of the knee, if the patient’s ASIS measures 23 cm to the tabletop, how will you direct your CR?

Perpendicular entering 1/2” distal to the apex of the patella

For the AP projection of the knee, how will the femoral condyles be positioned with respect to the IR?

parallel

How should the intercondylar eminence appear in the image of an AP projection of the knee if there is no rotation?

The intercondylar eminence should be centered

How should the fibular head appear with respect to the tibia in the image of a properly positioned AP projection of the knee?

Slightly superimposed

How should the patella appear in the image of an AP projection of the knee if there is no rotation?

The intercondylar eminence should be centered

How should the fibular head appear with respect to the tibia in the image of a properly positioned AP projection of the knee?

Completely superimposed on the femur

How should the femorotibial joint appear on the image of a properly positioned AP projection of the knee?

Open, with interspaces of equal width on both sides if the knee is normal

You take an image of the AP projection of the knee. You note that the fibular head is more than slightly superimposed, what is the error?

Knee rotated externally

You take an image of the AP projection of the knee. The fibular head is free of superimposition with the tibia. What is the error?

Knee rotated internally

For the lateral projection of the knee, how should the femoral condyles be positioned with respect to the IR?

perpendicular

How many degrees is the knee flexed for the lateral projection?

20-30 degrees

Max amount of flexion for a suspected patellar #

10 degrees

What is the CR for the lateral projection of the knee

5-7 degrees cephalad entering 1” distal to the medial epicondyle

How should the fibular head appear with respect to the tibia in a properly positioned lateral projection of the knee?

Open

How should the femorotibial joint be demonstrated in the image of a properly positioned lateral projection of the knee?

Open

You take a lateral projection of the knee. You note that the medial femoral condyle is more anterior than the lateral condyle. Which positioning error occurred?

Knee is externally rotated

You take a lateral projection of the knee. You note that the lateral femoral condyles is more anterior than the medial femoral condyle. Which positioning error occurred?

Knee is medially rotated

After imaging a lateral projection of the knee, you note that the medial femoral condyle is projected inferiorly to the lateral femoral condyles. What error occured?

Angle too small/no angle used

After imaging a lateral projection of the knee, you note that the medial femoral condyle is projected superiorly to the lateral femoral condyle. What error occurred?

Angle is too large

After imaging the lateral projection of the knee, you note that the tibia and fibular head have MORE than slight superimposition. Which positioning error occurred?

Knee internally rotated

After imaging the lateral projection of the knee, the tibia and fibular head are nearly free of superimposition. Which error occurred?

Knee is externally rotated