Spine: lumbar root signs: 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.

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Orthopaedics · Spine: lumbar root signs

Sample item

A patient with sciatica has weakness of ankle plantar flexion, loss of sensation over the lateral foot and a diminished ankle jerk. Which root is involved?

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

The answer and the reasoning

B. S1

S1 root compression causes weak plantar flexion and eversion, sensory loss on the lateral foot and little toe, and a diminished or absent ankle jerk. L5 compression causes weak great toe extension (EHL) and numbness over the dorsum, and L4 diminishes the knee jerk.

Option by option

  • A. L5

    L5 affects great toe extension, with no reflex change.

  • B. S1 (correct)

    Correct. The ankle jerk and plantar flexion belong to S1.

  • C. L4

    L4 affects the knee jerk and ankle dorsiflexion.

  • D. L3

    L3 affects knee extension and the knee jerk.

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.

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Questions about this Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is B, S1. S1 root compression causes weak plantar flexion and eversion, sensory loss on the lateral foot and little toe, and a diminished or absent ankle jerk.

Why is "L5" not the answer?

L5 affects great toe extension, with no reflex change.

Why is "L4" not the answer?

L4 affects the knee jerk and ankle dorsiflexion.

Why is "L3" not the answer?

L3 affects knee extension and the knee jerk.

What concept does this question test?

It tests Spine: lumbar root signs in Orthopaedics. L5 compression causes weak great toe extension (EHL) and numbness over the dorsum, and L4 diminishes the knee jerk.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Spine: lumbar root signs?

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.