Table of ContentsView AllTable of ContentsFunctionDeltoid HeadsProblems With DeltoidsRisk Factors for Deltoid Muscle ProblemsRehabilitationKeeping Deltoids Healthy
Table of ContentsView All
View All
Table of Contents
Function
Deltoid Heads
Problems With Deltoids
Risk Factors for Deltoid Muscle Problems
Rehabilitation
Keeping Deltoids Healthy
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.
The deltoid connects to theclavicle(collarbone), spine of thescapula(shoulder blade), andhumerus(upper arm bone).
Conditions that affect the deltoid muscle include rotator cuff injuries, nerve and blood vessel injuries, as well as strains, tendonitis, and shoulder infringement syndrome.
This article describes the anatomy of the deltoid muscle, as well as symptoms, treatment, and healing time for conditions affecting the deltoid muscle.
What Is the Function of the Deltoid Muscle?
Deltoid muscles are a type of skeletal muscle involved in body movements. Unlike smooth muscles, which are involuntary, skeletal muscles are voluntary (meaning you control them).
Each deltoid muscle is located where the ball-and-socket joint of your shoulder connects your humerus (upper arm bone) to your trunk.
The main functions of the deltoid muscles are to stabilize the shoulder joint and move the humerus at or through the shoulder. These muscle movements are referred to as:
The deltoid muscles have three heads that attach to bone and other tissue. Their origins—where the muscle attaches to a fixed point that does not move when the muscle contracts—are the clavicle and scapula. Theirinsertion—the point that attaches to a bone that moves—is 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.
Anatomy of the Shoulder Joint
What Are the Deltoid Heads?
Each of the three deltoid heads—anterior, lateral, posterior—enables different movements either on their own or together.
Anterior Deltoid
The anterior deltoid, located at the front of the shoulder, internally rotates the shoulder joint and moves the arm forward. 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 thepectoralis major muscleof the chest. The adjacent points help stabilize the shoulder.
Lateral Deltoid
The lateral deltoid, located in the middle of the shoulder, lifts the humerus to the side (laterally) away from the body. During abduction, the lateral deltoid moves downward to accommodate the arm’s outward movement.
The origin point of the lateral deltoid is at the outer tip of the scapula, which is known as theacromion process.
Posterior Deltoid
The posterior deltoid, located at the back of the shoulder, also rotates the joint laterally to move the arm outward and backward. During extension, the posterior deltoid allows the humeral head to rotate downward and inward in the socket of the joint.
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.
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What Conditions Affect the Deltoid Muscles?
The deltoid muscles are vulnerable to injuries that can affect not only the muscle but also connective tissues calledtendonsthat connect muscles to bones. Underlying nerves or blood vessels can also be injured.
Rotator Cuff Injuries
Therotator cuffis a group of muscles and tendons that surround the shoulder joint, keeping the head of the humerus firmly situated within the socket of the shoulder.
Arotator cuff tearis a common injury in which tendons are torn either partially or completely. Although the deltoid muscle isn’t one of the rotator cuff muscles, the destabilizing effect of a tear can place mechanical stress on the deltoid muscle, leading to a deltoidstrain.
Symptoms of a rotator cuff injury may include:
Treatment may include:
In some cases, treating a rotator cuff tear involves cutting through the deltoid muscle and then stitching it back together. 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.
Axillary Nerve Injury
Depending on the cause of the nerve injury, some people won’t need treatment. The injury may get better on its own. But surgery may be needed to repair the damage along with extensive rehabilitation to regain shoulder, arm, and hand strength.
The rate of recovery is different for everyone, but it can take many months to heal.
Vascular Injuries
Thecephalic veinis a blood vessel that runs beside the deltoid muscle down the arm to the hand. 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. The artery typically runs through a groove between the deltoid and pectoralis muscles, but, in some people, the vessel tunnels through the deltoid muscle itself.
In such cases, any injury to the deltoid muscle can also damage the thoracoacromial artery, causing nerve injury, pain, spasms, andmuscle atrophy(wasting) if not promptly treated.
Other Injuries
Other conditions that affect the deltoid muscle include:
Strains and overuse injuries:When muscle fibers get overstretched, it causes muscle strain, which can happen suddenly or develop gradually over time from overuse or repetitive movements. Symptoms may include pain and difficulty moving and lifting your arm.Depending on how severe the strain is, it can take a few weeks to several months to heal.
Tendonitis:When the tendons in the shoulder get inflamed, it results in shoulder tendonitis. Symptoms may include pain and tenderness in the shoulder and the inability to hold your arm in certain positions.Mild tendonitis may take just a few weeks to heal, while chronic tendonitis can take months to heal.
Shoulder impingement syndrome:This occurs when the shoulder muscles or tendons rub against bones. Symptoms include joint pain and inflammation.Depending on the extent of the injury, it can take three to six months or up to a year for this injury to heal.
Treatment for these injuries may include:
When to Call Your Healthcare Provider
You should call your healthcare provider if you have:
Although anyone can have problems with their deltoid muscles, your risk for shoulder problems increases if you:
What Is Involved in Rehabilitation?
If you have surgery or a severe injury involving the deltoid muscle, rehabilitation would typically involve an immobilizing shoulder brace to keep the arm still for at least two to three weeks.This gives the muscle ample time to heal and also prevents re-injury.
While the arm is immobilized, you would be encouraged to keep the elbow, wrist, and finger joints moving. Not doing so can lead to muscle stiffness in other areas and result in longer rehabilitation times.
You will likely start doing strength and range-of-motion exercises six weeks after surgery or injury under the guidance of yourorthopedic surgeonor aphysical therapist. Anoccupational therapistmay be recruited to help you manage or regain abilities such as dressing, writing, driving, or throwing.
Shoulder Rehabilitation Exercises
How Do You Keep Deltoid Muscles Healthy?
Not surprisingly, exercise is the best way to keep deltoid muscles healthy and reduce the risk of injury. This may involve resistance and weight training or, in older people or those with physical limitations, stretching and rotational exercises to keep joints and tendons flexible.
Exercises beneficial to the shoulders and deltoid muscles include:
In addition, there are certain habits that can prevent repetitive stress injuries to the shoulder (includingtendinitisandbursitis). This includes improving your general posture and not overdoing it with heavy weights at the gym or work.
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. Each head also has different insertion points and enables different movements known as abduction, flexion, extension, and rotation.
Contact a healthcare provider if you have shoulder pain that has lasted for weeks; trouble sleeping due to shoulder pain; or decreased range of motion in your arm.
14 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Dyrna F, Kumar NS, Obopilwe E, et al.Relationship between deltoid and rotator cuff muscles during dynamic shoulder abduction: a biomechanical study of rotator cuff tear progression.Am J Sports Med. 2018;46(8):1919-1926. doi:10.1177/0363546518768276Johns 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: StatPearls.Anatomy, shoulder and upper limb, deltoid muscle.Besharat S, Grol-Prokopczyk H, Gao S, Feng C, Akwaa F, Gewandter JS.Peripheral edema: A common and persistent health problem for older Americans.PLoS One. 2021;16(12):e0260742. doi:10.1371/journal.pone.0260742Bunker TD, Cosker TD, Dunkerley S, Kitson J, Smith CD.Anatomical variations of the deltoid artery: relevance to the deltopectoral approach to the shoulder.Bone Joint J. 2013;95-B(5):657-9. doi:10.1302/0301-620X.95B5.31408NYU Langone Health.Shoulder sprains and strains.Johns Hopkins Medicine.Shoulder tendonitis.National Library of Medicine StatPearls.Shoulder impingement syndrome.Tooth C, Gofflot A, Schwartz C, et al.Risk Factors of Overuse Shoulder Injuries in Overhead Athletes: A Systematic Review.Sports Health. 2020;12(5):478-487. doi:10.1177/1941738120931764van der Molen HF, Foresti C, Daams JG, Frings-Dresen MHW, Kuijer PPFM.Work-related risk factors for specific shoulder disorders: a systematic review and meta-analysis.Occup Environ Med. 2017;74(10):745-755. doi:10.1136/oemed-2017-104339Sadeghian F, Raei M, Amiri M.Persistent of Neck/Shoulder Pain among Computer Office Workers with Specific Attention to Pain Expectation, Somatization Tendency, and Beliefs.Int J Prev Med. 2014;5(9):1169-1177.PMID: 25317301American Academy of Orthopaedic Surgeons: OrthoInfo.Rotator cuff tears: Surgical treatment options.Icahn School of Medicine at Mount Sinai.Using Your Shoulder After Surgery.
14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Dyrna F, Kumar NS, Obopilwe E, et al.Relationship between deltoid and rotator cuff muscles during dynamic shoulder abduction: a biomechanical study of rotator cuff tear progression.Am J Sports Med. 2018;46(8):1919-1926. doi:10.1177/0363546518768276Johns 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: StatPearls.Anatomy, shoulder and upper limb, deltoid muscle.Besharat S, Grol-Prokopczyk H, Gao S, Feng C, Akwaa F, Gewandter JS.Peripheral edema: A common and persistent health problem for older Americans.PLoS One. 2021;16(12):e0260742. doi:10.1371/journal.pone.0260742Bunker TD, Cosker TD, Dunkerley S, Kitson J, Smith CD.Anatomical variations of the deltoid artery: relevance to the deltopectoral approach to the shoulder.Bone Joint J. 2013;95-B(5):657-9. doi:10.1302/0301-620X.95B5.31408NYU Langone Health.Shoulder sprains and strains.Johns Hopkins Medicine.Shoulder tendonitis.National Library of Medicine StatPearls.Shoulder impingement syndrome.Tooth C, Gofflot A, Schwartz C, et al.Risk Factors of Overuse Shoulder Injuries in Overhead Athletes: A Systematic Review.Sports Health. 2020;12(5):478-487. doi:10.1177/1941738120931764van der Molen HF, Foresti C, Daams JG, Frings-Dresen MHW, Kuijer PPFM.Work-related risk factors for specific shoulder disorders: a systematic review and meta-analysis.Occup Environ Med. 2017;74(10):745-755. doi:10.1136/oemed-2017-104339Sadeghian F, Raei M, Amiri M.Persistent of Neck/Shoulder Pain among Computer Office Workers with Specific Attention to Pain Expectation, Somatization Tendency, and Beliefs.Int J Prev Med. 2014;5(9):1169-1177.PMID: 25317301American Academy of Orthopaedic Surgeons: OrthoInfo.Rotator cuff tears: Surgical treatment options.Icahn School of Medicine at Mount Sinai.Using Your Shoulder After Surgery.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Dyrna F, Kumar NS, Obopilwe E, et al.Relationship between deltoid and rotator cuff muscles during dynamic shoulder abduction: a biomechanical study of rotator cuff tear progression.Am J Sports Med. 2018;46(8):1919-1926. doi:10.1177/0363546518768276Johns 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: StatPearls.Anatomy, shoulder and upper limb, deltoid muscle.Besharat S, Grol-Prokopczyk H, Gao S, Feng C, Akwaa F, Gewandter JS.Peripheral edema: A common and persistent health problem for older Americans.PLoS One. 2021;16(12):e0260742. doi:10.1371/journal.pone.0260742Bunker TD, Cosker TD, Dunkerley S, Kitson J, Smith CD.Anatomical variations of the deltoid artery: relevance to the deltopectoral approach to the shoulder.Bone Joint J. 2013;95-B(5):657-9. doi:10.1302/0301-620X.95B5.31408NYU Langone Health.Shoulder sprains and strains.Johns Hopkins Medicine.Shoulder tendonitis.National Library of Medicine StatPearls.Shoulder impingement syndrome.Tooth C, Gofflot A, Schwartz C, et al.Risk Factors of Overuse Shoulder Injuries in Overhead Athletes: A Systematic Review.Sports Health. 2020;12(5):478-487. doi:10.1177/1941738120931764van der Molen HF, Foresti C, Daams JG, Frings-Dresen MHW, Kuijer PPFM.Work-related risk factors for specific shoulder disorders: a systematic review and meta-analysis.Occup Environ Med. 2017;74(10):745-755. doi:10.1136/oemed-2017-104339Sadeghian F, Raei M, Amiri M.Persistent of Neck/Shoulder Pain among Computer Office Workers with Specific Attention to Pain Expectation, Somatization Tendency, and Beliefs.Int J Prev Med. 2014;5(9):1169-1177.PMID: 25317301American Academy of Orthopaedic Surgeons: OrthoInfo.Rotator cuff tears: Surgical treatment options.Icahn School of Medicine at Mount Sinai.Using Your Shoulder After Surgery.
Dyrna F, Kumar NS, Obopilwe E, et al.Relationship between deltoid and rotator cuff muscles during dynamic shoulder abduction: a biomechanical study of rotator cuff tear progression.Am J Sports Med. 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: StatPearls.Anatomy, shoulder and upper limb, deltoid muscle.
Besharat S, Grol-Prokopczyk H, Gao S, Feng C, Akwaa F, Gewandter JS.Peripheral edema: A common and persistent health problem for older Americans.PLoS One. 2021;16(12):e0260742. doi:10.1371/journal.pone.0260742
Bunker TD, Cosker TD, Dunkerley S, Kitson J, Smith CD.Anatomical variations of the deltoid artery: relevance to the deltopectoral approach to the shoulder.Bone Joint J. 2013;95-B(5):657-9. doi:10.1302/0301-620X.95B5.31408
NYU Langone Health.Shoulder sprains and strains.
Johns Hopkins Medicine.Shoulder tendonitis.
National Library of Medicine StatPearls.Shoulder impingement syndrome.
Tooth C, Gofflot A, Schwartz C, et al.Risk Factors of Overuse Shoulder Injuries in Overhead Athletes: A Systematic Review.Sports Health. 2020;12(5):478-487. doi:10.1177/1941738120931764
van der Molen HF, Foresti C, Daams JG, Frings-Dresen MHW, Kuijer PPFM.Work-related risk factors for specific shoulder disorders: a systematic review and meta-analysis.Occup Environ Med. 2017;74(10):745-755. doi:10.1136/oemed-2017-104339
Sadeghian F, Raei M, Amiri M.Persistent of Neck/Shoulder Pain among Computer Office Workers with Specific Attention to Pain Expectation, Somatization Tendency, and Beliefs.Int J Prev Med. 2014;5(9):1169-1177.PMID: 25317301
American Academy of Orthopaedic Surgeons: OrthoInfo.Rotator cuff tears: Surgical treatment options.
Icahn School of Medicine at Mount Sinai.Using Your Shoulder After Surgery.
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