Fractures and dislocations: dial test for posterolateral corner injury: practice question

A Orthopaedics question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Orthopaedics · Fractures and dislocations: dial test for posterolateral corner injury

Sample item

A patient with a knee injury is examined prone. External rotation of the tibia is more than 10 degrees greater than on the other side at 30 degrees of knee flexion, but equal at 90 degrees. What does this indicate?

AAn isolated posterior cruciate ligament tearBA medial collateral ligament tearCA combined posterior cruciate ligament and posterolateral corner injuryDAn isolated posterolateral corner injury

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. An isolated posterolateral corner injury

The dial test measures tibial external rotation at 30 and 90 degrees. Increased rotation at 30 degrees only localises the lesion to the posterolateral corner. If it is increased at both 30 and 90 degrees, the PCL is also torn. The lateral collateral ligament, popliteus tendon and popliteofibular ligament make up the corner.

Option by option

A. An isolated posterior cruciate ligament tear
An isolated PCL tear gives a posterior sag and a positive posterior drawer, with no change in rotation at 30 degrees.
B. A medial collateral ligament tear
An MCL tear is shown by valgus laxity and not by increased external rotation.
C. A combined posterior cruciate ligament and posterolateral corner injury
A combined injury would show increased rotation at 90 degrees as well.
D. An isolated posterolateral corner injury (correct)
Correct. Increased external rotation at 30 degrees alone localises the injury to the posterolateral corner.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is D, An isolated posterolateral corner injury. The dial test measures tibial external rotation at 30 and 90 degrees.

Why is "An isolated posterior cruciate ligament tear" not the answer?

An isolated PCL tear gives a posterior sag and a positive posterior drawer, with no change in rotation at 30 degrees.

Why is "A medial collateral ligament tear" not the answer?

An MCL tear is shown by valgus laxity and not by increased external rotation.

Why is "A combined posterior cruciate ligament and posterolateral corner inju…" not the answer?

A combined injury would show increased rotation at 90 degrees as well.

What concept does this question test?

It tests Fractures and dislocations: dial test for posterolateral corner injury in Orthopaedics. Increased rotation at 30 degrees only localises the lesion to the posterolateral corner. If it is increased at both 30 and 90 degrees, the PCL is also torn. The lateral collateral ligament, popliteus tendon and popliteofibular ligament make up the corner.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Fractures and dislocations: dial test for posterolateral corner injury?

Pair each fracture with its classic complication and nerve injured. Then use the flashcards and the other Orthopaedics questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.