Difference Between Deltoid and Rotator Cuff

The key difference between deltoid and rotator cuff is that the deltoid cuff is a single muscle while the rotator cuff is a group of muscles and tendons located in the shoulders.

The deltoid cuff is a large muscle that consists of three muscle fibers. They are the anterior, posterior and intermediate muscle fibers. The rotary cuff is a muscle that consists of four muscles. They are supraspinatus muscle, infraspinatus muscle, teres minor muscle, and subscapularis muscle. Both deltoid cuff and rotator cuff play important roles in the rotation, abduction, and stability of shoulders.

CONTENTS

1. Overview and Key Difference
2. What is Deltoid Cuff
3. What is Rotator Cuff
4. Similarities Between Deltoid and Rotator Cuff
5. Side by Side Comparison – Deltoid vs Rotator Cuff in Tabular Form
6. Summary

What is Deltoid Cuff?

The deltoid cuff is a triangular muscle that forms the round contour of the shoulder. It consists of three muscle fibers. They are anterior or clavicular fibers, posterior or scapular fibers, and intermediate or acromial fibers. They are also known as anterior deltoids, posterior deltoids and lateral or medial deltoids, respectively. The deltoid cuff allows abduction and stabilization of shoulder joints. It also facilitates other movements and rotations of the shoulder. The anterior deltoids allow the pectoralis major to flex the shoulder. Pectoralis major is a thick muscle located in the chest. The anterior deltoid also works with subscapularis to rotate the humerus. The posterior deltoids allow the extension of shoulders. The infraspinatus muscle and teres minor muscle (in rotator cuff) also work with posterior deltoids for the extension as well as the rotation of shoulders. The lateral deltoids perform shoulder abduction during rotation.

The deltoid cuff injuries are caused by wearing and tearing of muscles, fatty atrophy and enthesopathy. Deltoid cuff tears are usually caused by shoulder dislocation or rotator cuff tears. Fatty atrophy includes aging, disuse of shoulders, lack of necessary nutrients, and muscular dystrophy. Enthesopathy is due to mechanical stress in the shoulders.

What is Rotator Cuff?

The rotator cuff is a group of muscles and tendons in the shoulder. These act as stabilizers in the shoulder. Rotator cuffs allow movements in the shoulders and maintain shoulder joint stability. Scapulohumeral muscles possess seven muscles that connect the humerus to the scapula. Out of these seven muscles, four muscles make up the rotator cuff. These include the supraspinatus muscle, infraspinatus muscle, teres minor muscle and the subscapularis muscle. All four muscles allow the function of rotation in the shoulders. These muscles begin from the scapula and connect to the head of the humerus. This forms a cuff at the shoulder joint. Thus, it performs multiple functions, including abduction, internal rotation and external rotation of the shoulders.

Rotator cuff injuries are caused by forcefully pulling motions or overhead motions. Such injuries are common in athletes, weightlifters, rugby players, tennis players, fast bowlers, and firefighters. This causes wear and tear in muscles and tendons. The most commonly injured muscle is the supraspinatus muscle.

What are the Similarities Between Deltoid and Rotator Cuff?

• Deltoid cuff and rotator cuff are two muscles located in the shoulder.
• They facilitate the stabilization, rotation, abduction, and other movements of the shoulder.

What is the Difference Between Deltoid and Rotator Cuff?

Despite both being muscles located in the shoulder, deltoid cuff is one muscle, while rotator cuff consists of four muscles and tendons. So, this is the key difference between deltoid and rotator cuff. Moreover, deltoid cuff injuries are usually caused by wearing and tearing of muscles, fatty atrophy and enthesopathy. But rotator cuff injuries are mainly caused by forcefully pulling motions or overhead motions.

The below infographic summarizes the differences between deltoid and rotator cuff in tabular form.

Summary – Deltoid vs Rotator Cuff

The deltoid cuff is a large triangular muscle that forms the round contour of the shoulder. The rotator cuff is a group of muscles and tendons in the shoulder. The deltoid cuff is a single muscle that consists of three types of muscle fibers while the rotator cuff is made up of four types of muscles of scapulohumeral muscles. Thus, this is the key difference between deltoid and rotator cuff. Both deltoid cuff and rotator cuff involve in the movement and the stability of shoulder joints. Both muscle injuries cause pain at the back of your shoulders, difficulty in lifting the arm and tightness in your shoulder. The prevention methods of such injuries are good rest, maintaining a good posture, stretching and minor exercises.

Reference:

1. Elzanie, A. (2020, August 22). Anatomy, shoulder and Upper LIMB, Deltoid Muscle. Retrieved May 08, 2021, Available here.
2. Hecht, M. (2019, November 26). Rotator cuff anatomy: Muscles, function, and pictures. Retrieved May 08, 2021, Available here.

Image Courtesy:

1. “Anatomy of rotator cuff” By George S. Athwal, MD April D. Armstrong, MD – (CC BY-SA 4.0) via Commons Wikimedia
2. “Deltoid muscle back” By Anatomography – en: Anatomography (setting page of this image) (CC BY-SA 2.1 jp) via Commons Wikimedia