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Muscles in the Arm

By Amelia Son, PTA

What are the Arm Muscles?

The arm muscles can be broken into the upper arm, which is the space between the shoulder and the elbow, and the lower arm, which is the space between the elbow and the wrist.  The following will describe both the upper and lower arm muscles, their function, and common injuries.

The upper arm has four main muscles, three on the anterior (front) side and one on the posterior (back) side.  They are as follows;

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

Shoulder muscles Labeled

  • Biceps Brachii – Anterior
    • Located on the anterior side of the upper arm
    • The two-headed muscle that sits in front of your humerus bone
    • The biceps brachii rotates the forearm as well as flexes the arm at the elbow and shoulder
    • The most common injuries are a strain to the biceps brachii and tearing of one of the two tendons that attach near the shoulder
  • Coracobrachialis – Anterior
    • Located under the biceps and closer to the humerus bone.
    • Please read this article on Proximal Humerus Fractures. 
    • This muscle lifts the arm from the shoulder and helps pull the arm back down to your side from a lifted position
    • The most common injuries are tendon ruptures
  • Brachialis – Anterior
    • Located under the biceps muscle but closer to, and crosses, the elbow joint
    • This muscle flexes the elbow
    • Common injuries are tendon ruptures, which could decrease the ability to bend at the elbow
  • Triceps Brachii – Posterior
    • A three-headed muscle that spans the back of the arm and crosses the elbow joint
    • This muscle straightens the arm at the elbow
    • Common injuries are muscle strains and tears

To learn more about the anatomy of the shoulder, please watch this VIDEO.

Muscles of the arm, bicep and tricep labeled. JOI Rehab

Muscles of the arm

Muscles in the Forearm

There are many muscles in the forearm for many different purposes.  There are also layers to the forearm’s anterior and posterior sides and are known as the superficial, intermediate, and deep layers.  The flexor surface muscle contains the pronator teres, flexor carpi radialis longus, the palmaris longus, the flexor carpi ulnais, and flexor digitorum superficialis.

With the majority of the muscles that cross into the hand and move the fingers, there are often injuries made from cutting or breaking the wrist.  When this happens, surgery is common to repair the tendons, and extensive hand therapy must reach full use.

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Written by: Amelia Son, PTA


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