An AP knee projection on a patient with an ASIS to tabletop measurement of 17 cm was obtained using a perpendicular central ray. The resulting image will demonstrate
A) an open knee joint.
B) an elongated fibular head.
C) the fibular head more than 0.5 inch (1.25 cm) from the tibial plateau.
D) the anterior tibial margin distal to the posterior tibial margin.

Question

Quizplus · Accepted Answer

The fibular head more than 0.5 inch (1.25 cm) from the tibial plateau is a common indication that the central ray was perpendicular for an AP knee projection, especially in patients with an ASIS to tabletop measurement of 17 cm, which suggests a certain amount of soft tissue thickness that requires proper beam alignment to avoid superimposition of structures.

An AP Knee Projection on a Patient with an ASIS