Organ system anatomy · USMLE Step 1

A patient is unable to extend the trunk and maintain posture. Which back muscle is primarily responsible for this action?

  1. Latissimus dorsi
  2. Trapezius
  3. Erector spinae
  4. Rhomboid major
Show answer and explanation

Correct answer: Erector spinae

The erector spinae muscle group extends the vertebral column and maintains erect posture. Weakness impairs trunk extension.

Difficulty: Medium Question 13 of 20

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