AP Knee

Question 1

• Should knee radiographs be taken with or without a grid? Why?

Answer 1

With grid because the knee is greater than 10 cm thickness

Question 2

• How should the femoral condyles be positioned in relation to the IR for a properly positioned AP knee?

Answer 2

Parallel to IR

Question 3

• What is the central ray location?

Answer 3

1.5” inferior to patellar apex

Question 4

• To properly demonstrate an open knee joints, what measurement should be taken to determine the central ray angle/direction?

Answer 4

Measure height from ASIS to IR. If less than 19cm angle 5-7 degrees caudad, if between 19cm-24cm, 0 angle, if greater than 24 cm angle 5-7 degrees cephalic.

Question 5

• What structures can be used to determine if there is any rotation in an AP knee?

Answer 5

Tibia and fibula - slight superimposition of proximal tibia over fibular head, separation of body
Femoral condyles - Symmetrical
Intercondylar eminence - center of knee