Paediatric: crescent sign in Perthes disease: 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 · Paediatric: crescent sign in Perthes disease

Sample item

A radiograph in a child with Legg-Calve-Perthes disease shows a subchondral radiolucent line in the femoral head. What does this crescent sign indicate?

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

The answer and the reasoning

A. Subchondral fracture, often an early sign of necrosis

The crescent sign is a subchondral fracture line beneath the necrotic epiphysis seen on the frog-leg lateral view in the early avascular stage. It signals the extent of necrosis and helps with classification.

Option by option

  • A. Subchondral fracture, often an early sign of necrosis (correct)

    Correct. The crescent sign indicates a subchondral stress fracture.

  • B. Septic arthritis

    Septic arthritis does not cause a crescent sign.

  • C. Healed stage with remodelling

    Remodelling is the final healed stage.

  • D. Fragmentation stage with healing

    Fragmentation shows irregular lucent and sclerotic areas later.

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 A, Subchondral fracture, often an early sign of necrosis. The crescent sign is a subchondral fracture line beneath the necrotic epiphysis seen on the frog-leg lateral view in the early avascular stage.

Why is "Septic arthritis" not the answer?

Septic arthritis does not cause a crescent sign.

Why is "Healed stage with remodelling" not the answer?

Remodelling is the final healed stage.

Why is "Fragmentation stage with healing" not the answer?

Fragmentation shows irregular lucent and sclerotic areas later.

What concept does this question test?

It tests Paediatric: crescent sign in Perthes disease in Orthopaedics. It signals the extent of necrosis and helps with classification.

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 Paediatric: crescent sign in Perthes disease?

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.