The Muscles in the Shoulder

By Diana Cratem OTR/CHT

The Muscles in the Shoulder

What Makes the Shoulder a Different Joint?

The most mobile joint in the body, the shoulder, has the greatest kinematics to allow us to reach in a multiplane direction with dexterity and precision to perform all kinds of activities from basic ADLs (activities of daily living) to more complex tasks. Many muscles combined to play a part in stabilizing your shoulder and its movements.

JOI Rehab image of the anterior shoulder muscles and anatomy with labels for supraspinatus, long head of Biceps, subscapularis and subacromial bursae

Shoulder muscles

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 front of the 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?

Rotator Cuff Muscles

Rotator Cuff Repair

The rotator cuff is a common name of the group of muscles and tendons that surround the shoulder. 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 rotator cuff helps lift and rotate the arm.  To learn more, read this article on rotator cuff repairs. 

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.

Rotator Cuff Injuries

The Rotator cuff tends to have the most injuries, ranging from tendonitis to muscle tears. Rotator cuff tears are typically from a lifetime of wear and tear. Treatment includes a combination of anti-inflammatory medicines, steroid injections, and physical therapy. JOI physical therapists will set up a treatment plan to relieve pain and restore strength.

Surgery may be necessary if you experience pain at night or have difficulty raising your arm for reaching and lifting. Watch this VIDEO of how surgery helped Barbara get her life back.

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

Shoulder Pain Causes

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.   It is important to know the location of the pain and the motions that exacerbate the pain.

X-ray illustration showing a man with pain in his shoulder muscles. JOI Rehab

Image of X-Ray Shoulder Pain

Decreased range of motion in the shoulder muscles can be caused by:

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

What are Common Injuries of Muscles in the Shoulder?

sprains are a common injury of the muscles in the shoulder

Strains are a common injury of muscles in the shoulder

Whether lifting boxes, pushing a lawnmower, or throwing a ball, our shoulders are in constant motion. Because it is the most mobile joint in your body, it becomes more prone to injury. Typically, initial treatment involves a conservative approach of rest, ice, anti-inflammatories, and physical therapy.

  • Strains – tears or stretches a muscle or tendon
  • Sprains – tears or stretches of ligaments
  • Labrum tear – tear in the cartilage
  • Spasm – tightening of the muscles
  • Frozen shoulder – stiffness and pain in joints

Watch this VIDEO of a sleeper stretch to help improve range of motion for a frozen shoulder.  To schedule for physical therapy at one of the 12 JOI Rehab Centers, please call 904-858-7045.

Shoulder Doctors in Jacksonville

If you have recently had a shoulder surgery please watch this helpful video: Dressing the Upper Body After an Injury or Surgery

If you have shoulder pain, the Jacksonville Orthopaedic Institute has the answers! JOI offers the area’s top orthopaedic shoulder specialists and they are ready to help you. We treatment options from physical therapy and sports medicine, all the way to the most advanced surgical treatment interventions. Let JOI get you on the road to recovery!

To schedule an appointment with a JOI Orthopaedic Shoulder Specialist, call 904-JOI-2000, schedule online, or click the link below.

Book An Appointment with a JOI Physician.

Image of Book An Appointment with a JOI Physician Button.


Written by: Diana Cratem OTR/CHT


Skip to content