Anatomy Exam Muscles of the Rotator Cuff 2 — Questions and Answers
Question 1: Which rotator cuff muscle is primarily responsible for initiating abduction of the arm (first 15 degrees)?
- Supraspinatus (Correct answer)
- Deltoid
- Infraspinatus
- Subscapularis
Correct answer: Supraspinatus
The supraspinatus initiates abduction for the first 15 degrees before the deltoid becomes the primary mover.
Question 2: The infraspinatus muscle inserts onto which part of the greater tubercle of the humerus?
- Middle facet (Correct answer)
- Superior facet
- Inferior facet
- Lesser tubercle
Correct answer: Middle facet
The infraspinatus inserts onto the middle facet of the greater tubercle of the humerus.
Question 3: Which nerve innervates the teres minor muscle?
- Axillary nerve (Correct answer)
- Suprascapular nerve
- Lower subscapular nerve
- Upper subscapular nerve
Correct answer: Axillary nerve
The teres minor is innervated by the axillary nerve (C5, C6), specifically its posterior branch.
Question 4: A patient cannot internally rotate their arm against resistance. Which rotator cuff muscle is most likely injured?
- Subscapularis (Correct answer)
- Supraspinatus
- Teres minor
- Infraspinatus
Correct answer: Subscapularis
The subscapularis is the primary internal rotator among the rotator cuff muscles.
Question 5: What is the primary blood supply to the supraspinatus tendon's critical zone?
- Suprascapular artery (Correct answer)
- Anterior circumflex humeral artery
- Posterior circumflex humeral artery
- Thoracoacromial artery
Correct answer: Suprascapular artery
The suprascapular artery provides the main blood supply to the supraspinatus, though its 'critical zone' near the insertion is relatively avascular.
Question 6: Which rotator cuff muscle originates from the infraspinous fossa of the scapula?
- Infraspinatus (Correct answer)
- Teres minor
- Supraspinatus
- Subscapularis
Correct answer: Infraspinatus
The infraspinatus originates from the infraspinous fossa, which occupies most of the posterior scapular surface below the spine.
Question 7: During the 'lift-off test,' which rotator cuff muscle is specifically being assessed?
- Subscapularis (Correct answer)
- Supraspinatus
- Infraspinatus
- Teres minor
Correct answer: Subscapularis
The lift-off test (Gerber's test) specifically isolates the subscapularis by asking the patient to lift the dorsum of their hand off the lower back.
Anatomy Exam Muscles of the Rotator Cuff 2
Which rotator cuff muscle is primarily responsible for initiating abduction of the arm (first 15 degrees)?