Bone infection: triple deformity of the 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 infection: triple deformity of the knee

Sample item

A young adult has long-standing tuberculous arthritis of the knee with a painful stiff joint. Which combination of deformities is typical of advanced disease?

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

The answer and the reasoning

A. Flexion, posterior subluxation and external rotation of the tibia

Spasm of the hamstrings and destruction of the ligaments and cartilage produce the triple deformity: flexion, posterior subluxation of the tibia on the femur and external rotation of the tibia. It also occurs in other destructive arthritides. Recognising it helps planning of correction.

Option by option

  • A. Flexion, posterior subluxation and external rotation of the tibia (correct)

    Correct. Flexion with posterior subluxation and external rotation is the triple deformity.

  • B. Extension with anterior subluxation of the tibia

    Extension and anterior subluxation do not occur because hamstrings pull the tibia back.

  • C. Valgus with internal rotation of the tibia

    Valgus with internal rotation is not the typical pattern.

  • D. Hyperextension with genu recurvatum

    Recurvatum is not seen in tuberculous arthritis.

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, Flexion, posterior subluxation and external rotation of the tibia. Spasm of the hamstrings and destruction of the ligaments and cartilage produce the triple deformity: flexion, posterior subluxation of the tibia on the femur and external rotation of the tibia.

Why is "Extension with anterior subluxation of the tibia" not the answer?

Extension and anterior subluxation do not occur because hamstrings pull the tibia back.

Why is "Valgus with internal rotation of the tibia" not the answer?

Valgus with internal rotation is not the typical pattern.

Why is "Hyperextension with genu recurvatum" not the answer?

Recurvatum is not seen in tuberculous arthritis.

What concept does this question test?

It tests Bone infection: triple deformity of the knee in Orthopaedics. It also occurs in other destructive arthritides. Recognising it helps planning of correction.

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 infection: triple deformity of the 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.