The Four Rotator Cuff Muscles
The rotator cuff consists of four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis. 1
Anatomical Organization
The four rotator cuff muscles form a musculotendinous complex that provides dynamic stability to the glenohumeral joint 1:
Anterior Component
- Subscapularis: Located anteriorly in the rotator cuff complex, this muscle is responsible for internal rotation and anterior shoulder stabilization 2
Superior Component
- Supraspinatus: Positioned superiorly, this muscle initiates shoulder abduction and has a triangular footprint on the greater tuberosity with an average maximum medial-to-lateral length of 6.9 mm 2, 3
Posterior Components
- Infraspinatus: Located posteriorly with a trapezoidal footprint on the greater tuberosity (average maximum medial-to-lateral length of 10.2 mm), this muscle is responsible for external rotation 2, 3
- Teres minor: Also positioned posteriorly, this muscle assists with external rotation and presents negative (extensor) moment arms during shoulder flexion 2, 4
Functional Significance
These four muscles work together as force couples to maintain glenohumeral joint stability 5:
- Axial force couple: The anterior rotator cuff (subscapularis) balances forces with the posterior rotator cuff (infraspinatus and teres minor) 5
- Coronal force couple: The supraspinatus works with the deltoid to enable shoulder elevation 6
- Humeral head centering: All four muscles coordinate to keep the humeral head properly positioned within the glenoid fossa during arm motion 7
Clinical Relevance
Understanding the specific anatomy of these four muscles is essential for surgical planning, particularly in rotator cuff repairs where the infraspinatus footprint actually occupies substantially more area on the greater tuberosity than previously believed 3. This explains why infraspinatus muscle atrophy is frequently observed even in small to medium-size rotator cuff tears 3.