The Rotator Cuff Consists of Four Muscles
The rotator cuff is composed of four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis. 1
Anatomical Organization
The four rotator cuff muscles are positioned around the glenohumeral joint in a specific arrangement:
- Supraspinatus: Located superiorly 2
- Infraspinatus and teres minor: Positioned posteriorly 2
- Subscapularis: Located anteriorly 2
These four muscles form a musculotendinous rotator cuff that provides dynamic stability to the shoulder joint. 1
Functional Significance
The rotator cuff muscles work together to create balanced force couples that maintain glenohumeral joint stability:
- The anterior and posterior rotator cuff muscles create a balanced axial force couple across the glenohumeral joint 3
- The infraspinatus-teres minor complex functions as a major humeral head depressor and contributor to glenohumeral joint stability 4
- The subscapularis provides resistance to anteriorly directed forces and is essential for maintaining proper humeral head positioning within the glenoid fossa 2, 5
Clinical Relevance
Understanding that the rotator cuff comprises these four specific muscles is critical for:
- Surgical planning: Tears involving the supraspinatus and infraspinatus may benefit from muscle transfers using the latissimus or teres major 6
- Biomechanical assessment: Combined tears to the supraspinatus and infraspinatus result in significantly greater superior humeral head translation (1.6 mm at 30° and 4.8 mm at 60° of abduction) compared to the intact shoulder 4
- Rehabilitation strategies: Each muscle has distinct activation patterns and recruitment characteristics that must be addressed in therapy 5