Logan Steele
The deltoid muscle, often referred to as the '
| Characteristics | Values |
|---|---|
| Name | Deltoid Muscle, Common Shoulder Muscle, Delt |
| Shape | Triangular |
| Parts | Anterior or Clavicular (Front Delt), Posterior or Scapular (Rear Delt), Intermediate or Acromial (Side Delt) |
| Function | Shoulder Stabilizer, Shoulder Abduction, Shoulder Flexion, Shoulder Extension, Shoulder Adduction, Shoulder Internal Rotation, Shoulder External Rotation |
| Conditions/Injuries | Adhesive Capsulitis, Axillary Nerve Palsy, Bursitis, Tendonitis, Cachexia, Neuromuscular Disorders, Myopathies, Enthesitis, Calcific Tendinitis, Myositis, Infection, Tumors, Chronic Avulsion Injury, Axillary Neuropathies |
| Weight | 192 grams on average in a study of 30 shoulders, ranging from 84 grams to 366 grams |
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What You'll Learn
The deltoid muscle is a large triangular shoulder muscle
The deltoid muscle, often referred to as the 'delts' or ''delt', is a large, triangular-shaped shoulder muscle. It is called so because its shape resembles the inverted Greek letter delta. The deltoid is a common site for intramuscular injections, including vaccinations.
The deltoid muscle is a key shoulder stabilizer, preventing inferior glenohumeral joint displacement while bearing a heavy load, such as in deadlift exercises. It is also one of the main abductors of the shoulder, assisting in lifting the arm away from the body. When the three parts of the deltoid contract simultaneously, it can assist in abducting the arm past 15 degrees. The deltoid cannot initiate abduction because it contracts parallel to the humeral axis. However, throughout abduction, the anterior and posterior parts of the deltoid stabilize the arm, while the lateral segment assists in raising the arm from 15 to 100 degrees.
The deltoid muscle is made up of three distinct sets of muscle fibres: the anterior or clavicular part (commonly known as the front delt), the posterior or scapular part (known as the rear delt), and the intermediate or acromial part (known as the side delt). These three parts form a triangular muscle, with the anterior and posterior portions being unipennate and the lateral region being multipennate. The deltoid originates from the scapular spine, superior acromial surface, and lateral third of the clavicle, with a U-shaped proximal attachment mirroring the trapezius muscle's distal insertion.
The deltoid muscle is susceptible to various conditions and injuries, such as adhesive capsulitis (frozen shoulder), axillary nerve palsy, and bursitis. It is also important to note that any shoulder surgery can affect the deltoid muscles due to their proximity to the surface of the skin. Conditions affecting the deltoid muscles are more common in athletes who perform a lot of overhead arm movements, such as baseball pitchers, tennis players, and weightlifters.
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Deltoid muscle conditions and injuries
The deltoid muscle is a large, triangular-shaped muscle that gives the shoulder its rounded contour. It is a key shoulder stabilizer, allowing for a range of motions, from lifting the arm to putting on clothes. Deltoid muscles are susceptible to various conditions and injuries, which can cause pain, soreness, stiffness, and restricted mobility.
One common issue is a strain or tear in the deltoid muscle, often caused by overuse or injury. Athletes who perform repetitive overhead arm movements, such as baseball pitchers, tennis players, and weightlifters, are particularly at risk. Strains can also occur suddenly due to heavy lifting or accidents like trips and falls. The severity of a strain can vary, with mild strains causing muscle tightness and more severe cases resulting in pain, swelling, and restricted arm movement. Treatment for a mild strain may include adjusting exercise routines, reducing workout intensity, and using over-the-counter anti-inflammatories to manage inflammation and discomfort.
Another condition affecting the deltoid muscle is adhesive capsulitis, commonly known as a frozen shoulder. This occurs when the capsule surrounding the shoulder joint becomes thick and stiff, leading to pain, muscle spasms, and stiffness. Shoulder tendonitis is also a common issue, characterised by inflammation of the tendons in the shoulder, resulting in deltoid pain and difficulty moving the joint.
In some cases, deltoid muscles may be affected by surgery or nerve damage. Shoulder surgeries, such as rotator cuff repairs, can cut through the deltoid muscles, potentially causing axillary nerve damage and reduced arm mobility. Additionally, conditions like axillary nerve palsy can lead to shoulder weakness or numbness around the deltoid muscle due to nerve compression or damage during surgery or traumatic injury.
Other pathologies that may impact the deltoid muscle include enthesitis, calcific tendinitis, myositis, infection, tumours, and chronic avulsion injury. Deltoid muscle pain can also be caused by nearby pathologies, such as issues with the subdeltoid bursa, acromion, or distal clavicle. Furthermore, repeated shoulder muscle injections can lead to deltoid fibrosis, preventing the muscle from repairing itself and resulting in pain and loss of muscle strength and mobility.
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Deltoid strengthening exercises
The deltoid muscle, named for its resemblance to the inverted Greek letter delta, is a large, triangular-shaped muscle that forms the contour of the shoulder. It is a powerful muscle that is used in everyday activities like putting on clothes and athletic activities like swimming and tennis. The deltoid is susceptible to various conditions, including adhesive capsulitis (frozen shoulder), axillary nerve palsy, and bursitis. Athletes who perform overhead arm movements are particularly prone to deltoid issues.
To strengthen the deltoid muscles, consider the following exercises:
Wall Push
Stand with your back and elbow straight next to a wall. Gently push your arm to the side against the wall as hard as you comfortably can without causing pain. Hold for 5 seconds and repeat 10 times on each side, ensuring it is pain-free.
Dumbbell Weight Arm Raises
Using a suitable dumbbell weight, perform arm raises in the anterior, lateral, and posterior directions. Repeat 10 times on each side, ensuring it is pain-free.
Resistance Band Forward Raises, Lateral Raises, and Pullbacks
Using a resistance band, perform forward raises, lateral raises, and pullbacks. Repeat 10 times on each side, ensuring it is pain-free.
It is important to note that deltoid muscles are susceptible to strain and injury, especially with overhead arm movements. If you experience any pain or discomfort during these exercises, stop and consult a healthcare professional.
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Deltoid muscle and shoulder surgery
The deltoid muscle is a large triangular-shaped muscle that sits over the glenohumeral joint in the shoulder. It is made up of three distinct sections: anterior or clavicular, middle or acromial, and posterior or spinal. The deltoid muscle is responsible for abducting the arm and stabilising the humeral head, as well as assisting in forward elevation. This muscle is used in a variety of everyday activities, such as putting on clothes and carrying shopping bags, as well as athletic activities like swimming and netball.
Deltoid muscle injuries can occur due to overuse or strain, with athletes who perform a lot of overhead arm movements being particularly susceptible. These injuries can cause pain and tenderness in the shoulder, especially when lifting the arm. In some cases, a deltoid muscle tear may occur, resulting in swelling and bruising. Most deltoid muscle conditions can be treated non-surgically, with treatments such as ice or cold compresses to reduce inflammation, adjusting exercise routines, and over-the-counter anti-inflammatories.
However, in more severe cases of deltoid muscle tears or other serious injuries, surgery may be required. Shoulder surgery carries risks, including infection, bleeding, blood clots, and scar tissue formation. The deltoid muscle can be affected by shoulder surgery, as it often needs to be cut through during procedures such as rotator cuff repairs or tendon surgeries. This can result in axillary nerve damage, leading to reduced arm mobility, or blood vessel damage, causing edema (swelling) in the shoulder and upper arm.
To assess deltoid muscle function, a healthcare provider may ask the patient to lift their arm in different directions to observe the muscle contraction. Imaging exams, such as X-rays, MRIs, ultrasounds, or CT scans, may also be recommended to check for any bone fractures, dislocations, or tissue tears. If surgery is required, the healthcare provider will determine whether open surgery or minimally invasive arthroscopic shoulder surgery is the best approach.
Following surgery, patients may be advised to immobilise their shoulder with a sling or supportive garment and undergo deltoid strengthening exercises to improve muscle strength. These exercises may include gentle wall push exercises, dumbbell weight arm raises, or resistance band exercises, all performed within a pain-free range of motion.
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Deltoid muscle and axillary nerve
The deltoid muscle is a large triangular muscle that gives the shoulder its rounded contour. It originates from the scapular spine, superior acromial surface, and lateral third of the clavicle, and attaches to the deltoid tuberosity of the humerus. The deltoid acts as a shoulder stabilizer and assists in abducting the arm. It is a common site for intramuscular injections and vaccinations.
The axillary nerve is an upper extremity nerve that provides motor innervation to the deltoid and teres minor muscles. It is located in the axilla, posterior to the axillary artery and anterior to the subscapularis muscle. The axillary nerve exits the axilla at the inferior border of the subscapularis and divides into three terminal branches: the posterior terminal branch, which innervates the posterior aspect of the deltoid and teres minor; the anterior terminal branch, which innervates the anterior aspect of the deltoid; and the upper lateral cutaneous nerve of the arm, which innervates the skin over the inferior portion of the deltoid.
The deltoid muscle and its innervating axillary nerve can be injured during shoulder surgery or dislocation, resulting in reduced arm mobility and potential shoulder weakness or numbness. Axillary nerve damage can also occur through compression or traction injury, leading to localized neuropathy and causing pain, loss of movement, and weakness in the deltoid and teres minor muscles. Accurate Manual Muscle Testing (MMT) is necessary to assess the extent of axillary nerve damage and the patient's ability to retain a normal range of motion.
In summary, the deltoid muscle is a key shoulder stabilizer that provides the shoulder with its rounded contour, while the axillary nerve innervates the deltoid and teres minor muscles, providing motor and sensory functions. Injuries to either the deltoid muscle or the axillary nerve can result in reduced shoulder function and mobility.
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Frequently asked questions
The deltoid muscle, also known as the 'common shoulder muscle', is a large triangular-shaped muscle that forms the shoulder's rounded contour.
The deltoid muscle is located in the shoulder, running across most of it and lying over the glenohumeral joint.
The deltoid muscle is a key shoulder stabilizer. It is responsible for elevating the arm in the scapular plane and is used in many athletic activities such as swimming and tennis.
Common issues with the deltoid muscle include tendonitis, adhesive capsulitis (frozen shoulder), axillary nerve palsy, and bursitis. Deltoid injuries are more common in athletes who perform a lot of overhead arm movements, such as baseball pitchers and weightlifters.
