Deltoid and Rotator Cuff Muscles

Anatomy and Structure of the Deltoid Muscle

The deltoid muscle is a large, triangular muscle responsible for arm movement. It consists of three distinct heads: anterior, lateral, and posterior, each contributing to different types of motion.

Functions of the Deltoid Muscle

• Anterior Head: Flexes and internally rotates the arm.
• Lateral Head: Abducts the arm beyond 15 degrees.
• Posterior Head: Extends and externally rotates the arm.

Rotator Cuff Muscles

The rotator cuff comprises four muscles that stabilize the shoulder joint and allow a wide range of movements.

Components of the Rotator Cuff

• Supraspinatus: Initiates arm abduction.
• Infraspinatus: Enables external rotation of the arm.
• Teres Minor: Assists with external rotation and adduction.
• Subscapularis: Internally rotates the arm.

Common Injuries and Conditions

Both the deltoid and rotator cuff muscles are prone to injuries such as tears, tendinitis, and impingement syndromes, often caused by overuse or trauma.