Triceps Brachii

Overview

The triceps brachii is the large muscle group at the back of the upper arm. All three heads join into a common tendon at the elbow and work together to straighten the arm.

The long head begins on the scapula and crosses both the shoulder and elbow. The lateral and medial heads begin on the humerus and act primarily at the elbow. This arrangement lets the triceps generate force in pressing, throwing and pushing yourself up from a chair.

Location

• Covers most of the back of the upper arm
• Runs from the scapula and humerus to the point of the elbow
• Sits close to the radial nerve as that nerve wraps behind the humerus

The Three Heads

• Long head: begins below the shoulder socket and assists shoulder extension and adduction
• Lateral head: forms much of the visible outer-back contour of the upper arm
• Medial head: lies deeper and contributes across a wide range of elbow loads

Origin, Insertion, Nerve Supply, and Action

• Origin: Infraglenoid tubercle of the scapula and posterior humerus above and below the radial groove
• Insertion: Olecranon of the ulna through the common triceps tendon
• Nerve supply: Radial nerve, mainly C6–C8
• Action: Extends the elbow; the long head also assists shoulder extension and adduction

Function

• Straightens the elbow during pressing and throwing
• Controls elbow bending while lowering a load
• Helps support the body during push-ups, dips and transfers
• Assists the shoulder during pulling and forceful arm extension

Common Problems

• Muscle strain after forceful pressing or throwing
• Triceps tendinopathy near the back of the elbow
• Partial or complete distal triceps tendon tear
• Soreness after an unfamiliar increase in training volume

Pain at the back of the arm can also come from the neck, radial nerve or elbow joint. A painful movement does not identify the triceps by itself.

When to Get It Assessed

A sudden pop, rapid swelling, a palpable gap above the elbow or an inability to straighten the elbow against resistance may indicate a significant tendon injury and should be assessed promptly.

Related Anatomy

• Anconeus
• Humerus
• Radial nerve
• Overhead triceps and shoulder stretch

References

1. OpenStax. “Muscles of the Pectoral Girdle and Upper Limbs.” https://openstax.org/books/anatomy-and-physiology-2e/pages/11-5-muscles-of-the-pectoral-girdle-and-upper-limbs
2. StatPearls. “Anatomy, Shoulder and Upper Limb, Triceps Muscle.” https://www.ncbi.nlm.nih.gov/books/NBK536996/
3. Moore KL et al. Clinically Oriented Anatomy. Wolters Kluwer.