The Muscles in the Shoulder

By Diana Cratem OTR/CHT

 The Muscles in the Shoulder

Muscles in the shoulder

Muscles in the shoulder

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.

There are numerous muscles that give functionality to the shoulder. They support the upper extremity when in motion, and maintain the stability necessary for successful reaching.

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.

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 union with each other to keep stability of the shoulder joint. The rotator cuff muscles support the rounded humeral head and mechanically prevent it from excessively rolling while moving.

The Supraspinatus helps to support 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 also inserts into the humeral head, assisting the shoulder to externally rotate (throwing motion). The Teres Minor muscle sits below the Infraspinatus tendon and facilitates the external rotation as well. Further, the Subscapularis muscle is the most anterior muscle and facilitates internal rotation.

Due to the dynamics playing on the shoulder muscles, the Rotator cuff tends to have the most injuries, ranging from tendonitis to muscle tears.

Shoulder Injuries

Most shoulder consultations are due to shoulder pain. Some of them are simply caused by muscle inflammation due to mechanical stress of repetitive motion. A progressive degeneration can occur if the initial problem is not diagnosed and treated. Aging can also affect the muscles of the rotator cuff, due to narrowing of the joint spaces and poor posture (rounded shoulders). This could result in an increase in the degeneration of the tendons and cause tears. Some of these problems can be avoided by early intervention. With Physical/Occupational therapy can provide the patient with techniques and exercises to strengthen those muscles. Further, it is important to know the location of the pain and the emotions 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. Further, all of the above can be treated once diagnosed, so never delay your shoulder pain diagnosis. Our body sends us signs when one of its parts is not properly functioning.

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 that can help diagnosis 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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