010-111 · Question #16
Which rotator cuff muscle abducts the arm?
The correct answer is B. Supraspinatus. The supraspinatus is the only rotator cuff muscle that performs glenohumeral abduction, working synergistically with the deltoid. The remaining three rotator cuff muscles function primarily as humeral rotators or joint stabilizers.
Question
Which rotator cuff muscle abducts the arm?
Options
- AInfraspinatus
- BSupraspinatus
- CSubscapularis
- DMedial deltoid
How the community answered
(24 responses)- A4% (1)
- B75% (18)
- C13% (3)
- D8% (2)
Why each option
The supraspinatus is the only rotator cuff muscle that performs glenohumeral abduction, working synergistically with the deltoid. The remaining three rotator cuff muscles function primarily as humeral rotators or joint stabilizers.
The infraspinatus inserts on the middle facet of the greater tubercle and primarily performs external rotation of the humerus, not abduction.
The supraspinatus originates on the supraspinous fossa of the scapula and inserts on the superior facet of the greater tubercle of the humerus, producing abduction at the glenohumeral joint. It is especially active in initiating the first 15-30 degrees of abduction and continues to contribute throughout the full range of motion alongside the deltoid.
The subscapularis inserts on the lesser tubercle of the humerus and functions as the primary internal rotator of the shoulder, not an abductor.
The middle deltoid does contribute to arm abduction, but it is not a rotator cuff muscle - the rotator cuff is specifically defined as the supraspinatus, infraspinatus, teres minor, and subscapularis.
Concept tested: Rotator cuff muscle actions and glenohumeral abduction
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