Musculoskeletal anatomy · USMLE Step 1

A patient cannot flex the distal interphalangeal joint of the index finger. Which muscle is impaired?

  1. Flexor digitorum superficialis
  2. Flexor digitorum profundus
  3. Lumbrical muscle
  4. Flexor pollicis longus
Show answer and explanation

Correct answer: Flexor digitorum profundus

Flexor digitorum profundus is the only muscle that flexes the distal interphalangeal joints of the fingers; flexor digitorum superficialis flexes the PIP joints. The portion serving the index finger is innervated by the anterior interosseous nerve.

Difficulty: Medium Question 8 of 20

Practice all 20 Musculoskeletal anatomy questions

Keep practicing

More Musculoskeletal anatomy questions