Crystal arthropathy: 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 · Crystal arthropathy

Sample item

What do the crystals in synovial fluid of gout look like under polarised light?

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

The answer and the reasoning

B. Needle-shaped and negatively birefringent

Gout is caused by monosodium urate crystals, which are needle-shaped and negatively birefringent (yellow when parallel to the compensator axis). Pseudogout shows calcium pyrophosphate crystals, which are rhomboid and weakly positively birefringent.

Option by option

  • A. Rhomboid and positively birefringent

    Rhomboid, positively birefringent crystals indicate pseudogout.

  • B. Needle-shaped and negatively birefringent (correct)

    Correct. This is the diagnostic crystal appearance of gout.

  • C. Bipyramidal and non-birefringent

    Calcium oxalate crystals are bipyramidal.

  • D. Rectangular plates

    Cholesterol crystals are rectangular plates.

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, Needle-shaped and negatively birefringent. Gout is caused by monosodium urate crystals, which are needle-shaped and negatively birefringent (yellow when parallel to the compensator axis).

Why is "Rhomboid and positively birefringent" not the answer?

Rhomboid, positively birefringent crystals indicate pseudogout.

Why is "Bipyramidal and non-birefringent" not the answer?

Calcium oxalate crystals are bipyramidal.

Why is "Rectangular plates" not the answer?

Cholesterol crystals are rectangular plates.

What concept does this question test?

It tests Crystal arthropathy in Orthopaedics. Pseudogout shows calcium pyrophosphate crystals, which are rhomboid and weakly positively birefringent.

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 Crystal arthropathy?

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.