Bone and joint infections: tabetic Charcot knee: 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 · Bone and joint infections: tabetic Charcot knee

Sample item

A 58-year-old man has a grossly swollen, unstable right knee with a large painless effusion, crepitus and multiple loose bodies. He has small irregular pupils that accommodate but do not react to light, and absent ankle jerks. What is the underlying joint diagnosis?

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

The answer and the reasoning

D. Neuropathic arthropathy from tabes dorsalis

A painless, disorganised joint with debris and loose bodies in a patient with Argyll Robertson pupils and absent reflexes is a tabetic Charcot joint, the result of loss of protective sensation from neurosyphilis. The knee and hip are classically affected in tabes, the shoulder in syringomyelia and the tarsal joints in diabetes.

Option by option

  • A. Calcium pyrophosphate arthropathy

    Pseudogout is painful and episodic, with rhomboid crystals and chondrocalcinosis.

  • B. Haemophilic arthropathy

    Haemophilic arthropathy follows repeated haemarthroses in a boy with a bleeding disorder and is not painless.

  • C. Septic arthritis from Staphylococcus aureus

    Septic arthritis is acutely painful with fever and a hot joint.

  • D. Neuropathic arthropathy from tabes dorsalis (correct)

    Correct. Loss of position and pain sense in tabes dorsalis leads to a destroyed, painless joint.

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 D, Neuropathic arthropathy from tabes dorsalis. A painless, disorganised joint with debris and loose bodies in a patient with Argyll Robertson pupils and absent reflexes is a tabetic Charcot joint, the result of loss of protective sensation from neurosyphilis.

Why is "Calcium pyrophosphate arthropathy" not the answer?

Pseudogout is painful and episodic, with rhomboid crystals and chondrocalcinosis.

Why is "Haemophilic arthropathy" not the answer?

Haemophilic arthropathy follows repeated haemarthroses in a boy with a bleeding disorder and is not painless.

Why is "Septic arthritis from Staphylococcus aureus" not the answer?

Septic arthritis is acutely painful with fever and a hot joint.

What concept does this question test?

It tests Bone and joint infections: tabetic Charcot knee in Orthopaedics. The knee and hip are classically affected in tabes, the shoulder in syringomyelia and the tarsal joints in diabetes.

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 Bone and joint infections: tabetic Charcot knee?

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.