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The deltoid muscle is a large, thick, triangular-shaped muscle that covers the top of the shoulder. It is a common shoulder muscle, so-called because its shape resembles the inverted Greek letter delta. The deltoid is a key shoulder stabilizer, helping to move the arm in different directions and preventing inferior glenohumeral joint displacement. It is divided into three parts: the anterior or clavicular part (front delt), the posterior or scapular part (rear delt), and the intermediate or acromial part (side delt).
| Characteristics | Values |
|---|---|
| Name | Deltoid Muscle |
| Alternative Names | Common Shoulder Muscle, Delt, Deltoideus |
| Description | Large, triangular-shaped muscle |
| Location | Shoulder, Shoulder Joint, Upper Arm |
| Function | Shoulder abduction, flexion, extension, stabilisation, elevation |
| Blood Supply | Axillary Artery, Thoracoacromial Artery, Circumflex Humeral Arteries, Profunda Brachii Artery, Deep Brachial Artery |
| Innervation | Axillary Nerve |
| Anatomy | Three distinct parts: Anterior/Clavicular, Lateral/Acromial/Middle, Posterior/Spinal/Rear |
| Injuries | Tears, Strains, Rotator Cuff Tears, Axillary Nerve Injuries, Adhesive Capsulitis, Deltoid Fibrosis, Shoulder Impingement Syndrome |
| Exercises | Wall Pushes, Dumbbell Raises, Resistance Band Exercises |
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What You'll Learn
- The deltoid muscle is a large, triangular-shaped muscle in the shoulder and upper arm region
- It has three parts: anterior, lateral, and posterior
- The deltoid is responsible for arm abduction and flexion
- It is commonly injured by sports injuries, motor vehicle crashes, and repetitive actions
- Deltoid muscle tears are related to rotator cuff tears and shoulder dislocations
The deltoid muscle is a large, triangular-shaped muscle in the shoulder and upper arm region
The deltoid muscle is made up of three distinct sets of muscle fibres, each with a different origin: the anterior or clavicular part (commonly known as the front delt), the posterior or scapular part (commonly known as the rear delt), and the intermediate or acromial part (commonly known as the side delt). These three parts of the deltoid each have a different point of attachment, or "origin", to the shoulder: the anterior part attaches to the lateral third of the clavicle, the lateral part attaches to the acromion process, and the posterior part attaches to the spine of the scapula.
The deltoid muscle plays an important role in shoulder abduction, which is the movement of lifting the arm to the side of the body. Each part of the deltoid muscle can contract independently, producing different arm movements. For example, when the anterior deltoid contracts alone, it produces extension and lateral rotation of the arm. When the lateral part of the deltoid contracts independently, it causes the arm to abduct. Contraction of the posterior deltoid causes the arm to flex and medially rotate.
The deltoid muscle is susceptible to various injuries and conditions, such as tears, fatty atrophy, and enthesopathy. Deltoid muscle tears are uncommon but can occur during traumatic shoulder dislocations or massive rotator cuff tears. Muscle atrophy may result from ageing, disuse, denervation, muscular dystrophy, cachexia, and iatrogenic injury. Additionally, deltoid pain can be caused by repetitive overhead arm movements, such as swimming, pitching, or weightlifting.
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It has three parts: anterior, lateral, and posterior
The deltoid muscle, shaped like an inverted triangle, is located at the upper part of the arm and covers the glenohumeral and acromial joints. It is responsible for several functions, including abduction, medial and lateral rotation, and arm flexion and extension.
This muscle has three distinct parts: anterior, lateral, and posterior, each with its own specific origin, insertion points, and functions. The anterior portion, also known as the clavicular head or front part, originates from the anterior margin of the lateral third of the clavicle. It inserts into the anterior deltoid area of the humerus and is responsible for flexion and medial rotation of the arm.
The lateral portion, also referred to as the acromial part or the lateral head, originates from the inferior margin of the spine of the scapula and the superior margin of the lateral acromion. It inserts into the lateral deltoid area of the humerus and is responsible for the abduction of the arm.
The posterior portion, or the spinal head, originates from the lower margin of the spine of the scapula. It inserts into the posterior deltoid area of the humerus and is responsible for the extension and lateral rotation of the arm.
Together, these three parts of the deltoid muscle work in a coordinated manner to provide a wide range of movements and stability to the shoulder joint, allowing for various functional and athletic activities. Understanding the anatomy and functions of these muscle parts is crucial for athletes, fitness enthusiasts, and medical professionals for optimizing performance, preventing injuries, and facilitating effective rehabilitation.
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The deltoid is responsible for arm abduction and flexion
The deltoid muscle is a large, triangular-shaped muscle that forms the rounded contour of the shoulder. It is also known as the 'common shoulder muscle' and is one of the six intrinsic muscles of the shoulder. The deltoid muscle is responsible for arm abduction and flexion, which means it helps lift the arm to the front, side and back. This muscle is activated when carrying heavy weights, preventing dislocation of the glenohumeral joint.
The deltoid muscle can be divided into three parts: the anterior or clavicular, the lateral or acromial, and the posterior or spinal. Each of these parts attaches to a different region of the shoulder. The anterior part attaches to the lateral third of the clavicle, the lateral part attaches to the acromion process, and the posterior part attaches to the spine of the scapula. When these three parts contract simultaneously, it results in abduction of the shoulder when the arm is already held at 15 degrees of abduction.
The anterior deltoid is responsible for flexion, internal rotation, and horizontal adduction of the arm. This means it helps move the arm forward and is used when reaching for an object on a shelf. The lateral deltoid helps move the arm out to the side, as well as up and down. These side deltoids are used when doing jumping jacks. The posterior deltoid helps move the arm backward and is used when pitching a baseball.
The deltoid muscle is a powerful muscle that is used in many everyday activities such as putting clothes on a line, carrying shopping bags, and washing hair. It is also used in athletic activities such as netball, swimming, and water polo. The deltoid muscle can become injured by repeated overhead activities, sports injuries, and motor vehicle crashes, which can lead to tears or strains. Deltoid muscle tears are uncommon but can be related to massive rotator cuff tears or traumatic shoulder dislocations.
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It is commonly injured by sports injuries, motor vehicle crashes, and repetitive actions
The deltoid muscle is a large, triangular-shaped muscle that forms the shoulder's rounded contour. It is responsible for lifting the arm and helping the shoulder to move. It is one of the main abductors of the shoulder, activated when carrying heavy weights to prevent dislocation of the glenohumeral joint.
The deltoid is a powerful muscle, and its strength makes it susceptible to sports injuries, motor vehicle crashes, and repetitive actions. Sports injuries commonly affect the deltoid muscle, especially in sports that involve repeated overhead activities such as water polo, swimming, baseball, and netball. The deltoid is also vulnerable to injury during motor vehicle crashes, which can lead to tears or strains.
Repetitive actions, such as those performed by house painters, swimmers, water polo players, and pitchers, can cause deltoid pain and even injury. Overuse of the deltoid muscle can lead to strains, tightness, and pain. This can be prevented by warming up sufficiently, taking rest days, and using proper safety equipment. Sports massages and advice from sports therapists can also help prevent injuries.
In addition to sports injuries and repetitive actions, the deltoid muscle can be injured by repetitive intramuscular injections of vaccines, antibiotics, and other medications. Furthermore, injuries to the axillary nerve, such as those caused by humeral fractures, shoulder dislocations, or mechanical stress, can affect the functioning of the nerve and, consequently, the deltoid muscle.
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Deltoid muscle tears are related to rotator cuff tears and shoulder dislocations
The deltoid muscle is a large, triangular-shaped muscle that forms the rounded contour of the human shoulder. It is also referred to as the 'common shoulder muscle'. The deltoid muscle is one of the main abductors of the shoulder, helping to lift the arm when reaching for objects or brushing hair. It is activated when carrying heavy weights, such as a suitcase or grocery bags, to prevent dislocation of the glenohumeral joint. The deltoid muscle is composed of three distinct sets of muscle fibres: the anterior or clavicular part (commonly known as the front delt), the posterior or scapular part (commonly known as the rear delt), and the intermediate or acromial part (commonly known as the side delt).
Deltoid muscle tears are uncommon but are frequently associated with massive rotator cuff tears or traumatic shoulder dislocations. When a rotator cuff tear occurs, it places more strain on the deltoid to prevent abduction motion loss. The rotator cuff is a group of four muscles that come together as tendons to form a covering around the head of the humerus, attaching the humerus to the shoulder blade and enabling the arm to be lifted and rotated. A tear in the rotator cuff can cause partial or complete detachment of the tendon from the head of the humerus. This type of tear often occurs with other injuries, such as a dislocated shoulder.
In the case of shoulder dislocations, the axillary nerve may be injured, leading to paralysis of the deltoid muscle. The axillary nerve supplies the deltoid muscle and can be damaged during surgical procedures, such as breast cancer surgery, or by anterior dislocation of the head of humerus. Symptoms of axillary nerve injury include paralysis and atrophy of the deltoid muscle, resulting in loss of muscle tone and a flat-appearing shoulder.
Deltoid muscle tears can also be caused by repeated overhead activities, sports injuries, and motor vehicle crashes. Certain occupations and sports are associated with a higher risk of deltoid muscle injuries due to the repetitive overhead arm movements involved. These include automotive work, assembly line work, baseball pitching, tennis, and weightlifting. Additionally, individuals between the ages of 40 and 60, females, and those with specific health conditions, such as diabetes or rheumatoid arthritis, are at an increased risk for shoulder muscle conditions.
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Frequently asked questions
The deltoid muscle is located in the shoulder.
The deltoid muscle is a large, triangular-shaped muscle.
The deltoid muscle helps to lift the arm to the front, side and back, and is a key shoulder stabiliser.
The deltoid muscle is made up of three distinct parts: the anterior, lateral and posterior.
Common deltoid muscle injuries include tears, strains and overuse injuries.
