The deltoid muscle is the main muscle of the shoulder.
A triangle-shaped muscle, it helps move your upper arm and stabilizes the shoulder joint.
What Is the Function of the Deltoid Muscle?
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Deltoid muscles are a throw in of skeletal muscle involved in body movements.
Unlike smooth muscles, which are involuntary, skeletal muscles are voluntary (meaning you control them).
Theirinsertionthe point that attaches to a bone that movesis the humerus.
Together, these points help stabilize the shoulder joint and allow for a fullrange of motionof the upper arm.
The deltoid muscle is a common place to give drug and vaccine injections because it’s easy to access.
What Are the Deltoid Heads?
Each of the three deltoid headsanterior, lateral, posteriorenables different movements either on their own or together.
It does so with a combination of flexion and medial rotation (rotating of a joint inward).
The origin point of the anterior deltoid is on the clavicle alongside the pectoralis major muscle of the chest.
The adjacent points help stabilize the shoulder.
During abduction, the lateral deltoid moves downward to accommodate the arm’s outward movement.
The origin point of the posterior deltoid is on the part of the scapula known as the spine.
This prominent ridge also serves as an origin point for several other muscles.
This attachment both stabilizes and prevents the overextension of the shoulder joint.
What Conditions Affect the Deltoid Muscles?
Underlying nerves or blood vessels can also be injured.
Arotator cuff tearis a common injury in which tendons are torn either partially or completely.
This means you will need to rehabilitate the deltoid muscle along with the repaired rotator cuff.
The healing time for a rotator cuff injury varies depending on the size of the tear.
If surgery is required, it takes six to nine months before it’s completely healed.
The injury may get better on its own.
The rate of recovery is different for everyone, but it can take many months to heal.
It assists with circulation and fluid management within the muscle tissues.
An injury to the cephalic vein can result in fluid buildup in the upper arm, known asperipheral edema.
This can cause pain and weakness and limit your range of motion.
Thethoracoacromialartery is another blood vessel that directly services all three deltoid heads.
Tendonitis:When the tendons in the shoulder get inflamed, it results in shoulder tendonitis.
Shoulder impingement syndrome:This takes place if the shoulder muscles or tendons rub against bones.
Not doing so can lead to muscle stiffness in other areas and result in longer rehabilitation times.
How Do You Keep Deltoid Muscles Healthy?
Summary
The deltoid is the main muscle in the shoulder.
It is made up of three heads called the anterior, lateral, and posterior deltoids.
All three heads help move the arm and stabilize the shoulder joint.
The deltoid muscle can be injured or impacted by surgery either directly or indirectly.
In such cases, rehabilitation may be needed to restore flexibility, range of motion, and strength.
National Library of Medicine.Anatomy, shoulder and upper limb, deltoid muscle.
2018;46(8):1919-1926. doi:10.1177/0363546518768276
Johns Hopkins Medicine.Rotator cuff injury.
Penn Medicine, The Trustees of the University of Pennsylvania.What is axillary nerve disorder?
National Institutes of Health, U.S, National Library of Medicine.Anatomy, shoulder and upper limb, deltoid muscle.
2021;16(12):e0260742.
2024;16. doi:10.52965/001c.115352
NYU Langone Health.Shoulder sprains and strains.
Johns Hopkins Medicine.Shoulder tendonitis.
National Library of Medicine.Shoulder impingement syndrome.
University of Utah Health.When to see an orthopedic doctor for shoulder & elbow pain.
Icahn School of Medicine at Mount Sinai.Using your shoulder after surgery.
American Academy of Orthopaedic Surgeons: OrthoInfo.Rotator cuff and shoulder conditioning program.
2023;57(7):408-416. doi: 10.1136/bjsports-2022-105674
