What muscles control the rotator cuff?

Rotator Cuff Muscles

The rotator cuff is controlled by four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis, which together form a musculotendinous unit that provides dynamic stability to the shoulder joint. 1

Anatomical Organization

The four rotator cuff muscles are positioned around the glenohumeral joint in a specific arrangement:

• Supraspinatus is located superiorly and is responsible for initiating arm abduction 1
• Infraspinatus and teres minor are positioned posteriorly and function as external rotators and humeral head depressors 2, 3
• Subscapularis is located anteriorly and serves as the primary internal rotator 2, 1

Functional Biomechanics

These four muscles work together to maintain glenohumeral joint stability through coordinated force couples:

• The rotator cuff muscles provide dynamic centering of the humeral head within the glenoid fossa during shoulder movement 4, 1
• An axial force couple exists between the anterior (subscapularis) and posterior (infraspinatus and teres minor) rotator cuff muscles to balance forces across the joint 5
• The supraspinatus, external rotators, and scapular stabilizers experience repetitive eccentric stress during overhead activities, particularly in throwing athletes 6

Clinical Significance

Understanding the individual muscle contributions is essential for diagnosis and rehabilitation:

• The infraspinatus-teres minor complex functions as a major humeral head depressor, with combined tears to supraspinatus and infraspinatus causing significant superior humeral head migration (4.8 mm at 60° abduction) 3
• The subscapularis demonstrates consistently higher activation levels than infraspinatus and teres minor combined at the start of shoulder exercises and in end ranges of motion, suggesting its role in resisting anteriorly directed forces 7
• Rotator cuff weakness combined with ligamentous laxity, particularly in younger athletes, predisposes to secondary impingement syndrome 4

Rehabilitation Implications

Strengthening programs must address all four rotator cuff muscles along with scapular stabilizers:

• Treatment of rotator cuff dysfunction requires strengthening of the dynamic and scapular stabilizers of the shoulder, not just the four primary rotator cuff muscles 6
• Rehabilitation should emphasize proper coordination of scapular movements (upward rotation and posterior tilting during arm elevation) to prevent impingement 6, 4
• Muscular imbalance between weakened posterior shoulder musculature and overdeveloped anterior musculature leads to abnormal biomechanics and injury risk 6, 4