The Muscles in the Shoulder

By Diana Cratem OTR/CHT


Shoulder muscles and muscles of the shoulder and arm.

What Makes the Shoulder a Different Joint?

The body was beautifully and wonderfully made, with every part specifically designed to accomplish a task. The most mobile joint in the body, the shoulder, has the greatest kinematics to allow us to reach on a multiplane direction with dexterity and precision to perform all kinds of activities from basic ADL’s (activities of daily living) to more complex tasks.

Numerous muscles give functionality to the shoulder. They support the upper extremity when in motion and maintain the stability necessary for successful reaching.

What are the Muscles in the Front of the Shoulder?

The muscles in the front of the shoulder (anterior) include the Pectoralis Major and Minor, Subclavius, and Serratus Anterior. They are in charge of the arm flexion (reaching in front), adduction (reaching across), rotation, and depression of the scapula. The posterior shoulder is divided into two groups, the extrinsic and intrinsic muscles. The extrinsic layer is made up of the Latissimus Dorsi, Levator Scapula, and Rhomboid muscles, which are in charge of internal rotation (reaching in the back) and adduction. The intrinsic muscles include the rotator cuff muscles, Teres Major and Deltoid, which are in charge of rotations, flexion, and abduction.

What Are the Rotator Cuff Muscles?

The well-known term rotator cuff is a group of muscles formed by four muscles. The Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis work in unison to keep the shoulder joint’s stability. The rotator cuff muscles support the rounded humeral head and mechanically prevent it from excessively rolling while moving.

The Supraspinatus supports the humeral head within the glenoid (socket) by preventing subluxation and initiating the motion in abduction (reaching to the side). The Infraspinatus muscle originates in the back of the scapula area and inserts into the humeral head, assisting the shoulder to rotate (throwing motion) externally. The Teres Minor muscle sits below the Infraspinatus tendon and facilitates the external rotation as well. The Subscapularis muscle is the most anterior and facilitates internal rotation.

The Rotator cuff tends to have the most injuries, ranging from tendonitis to muscle tears.

To learn more about Rotator Cuff Injuries, watch this VIDEO by Dr. Kevin Kaplan of the Jacksonville Orthopedic Institute.

Why Do People Get Shoulder Pain?

Most shoulder consultations are due to shoulder pain. Some are caused by muscle inflammation due to mechanical stress of repetitive motion or the arm’s prolonged position above the body. A progressive degeneration can occur if the initial problem is not diagnosed and treated. Aging can also affect the rotator cuff muscles due to the narrowing of the joint spaces and poor posture (rounded shoulders). This could increase the degeneration of the tendons and cause tears. Some of these problems can be avoided by early intervention and Physical/Occupational therapy.  It is important to know the location of the pain and the motions that exacerbate the pain.

The decreased range of motion in the shoulder muscles can be caused by bursitis (inflammation of the bursa), adhesive capsulitis (frozen shoulder), fractures, muscle tears (partial or complete), muscle atrophy, or arthritis. All of the above can be treated once diagnosed, so never delay your shoulder pain diagnosis because even though we are wonderfully and perfectly made, our body sends us signs when one of its parts is not properly functioning.

If you would like to learn more about shoulder impingement, watch this VIDEO by Dr. Stephen Lucie of JOI.


JOI Fracture and Injury Care

JOI Physicians are currently offering ASAP fracture and injury care. Further, this is a new option for patients who would like to avoid the emergency room if they have suffered a fracture or soft tissue injury. To learn more about this service, read this article about fracture and injury care. Make an appointment by calling (904)JOI-2000.

Please do not hesitate to call JOI for your medical needs. Further, we have surgeons who can help diagnose your tear and therapy staff, waiting to help rehab you back to full health! Please call JOI-2000 or click the banner below to schedule with one of our specialists.


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Written by: Diana Cratem OTR/CHT


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