Musculoskeletal anatomy · USMLE Step 1

A patient presents with difficulty initiating shoulder abduction. Which muscle is primarily responsible for initiating the first 15 degrees of abduction?

  1. Deltoid
  2. Supraspinatus
  3. Infraspinatus
  4. Teres minor
Show answer and explanation

Correct answer: Supraspinatus

The supraspinatus initiates the first 15 degrees of shoulder abduction before the deltoid takes over. It is frequently injured in rotator cuff tears.

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