Radial Nerve

Q: Which forearm muscles are innervated by the deep branch of the radial nerve?

The deep branch of the radial nerve (r. profundus n. radialis) innervates several muscles of the posterior forearm compartment. These include: Supinator (m. supinator).Extensor digitorum (m. extensor digitorum).Extensor digiti minimi (m. extensor digiti minimi).Extensor carpi ulnaris (m. extensor carpi ulnaris).Abductor pollicis longus (m. abductor pollicis longus).Extensor pollicis brevis (m. extensor pollicis brevis).Extensor pollicis longus (m. extensor pollicis longus).

Nervus radialis

For medical students2 min readUpdated 2026-10-10

The radial nerve (nervus radialis) is a major nerve of the upper limb originating from the posterior cord of the brachial plexus. Its primary functional role is the innervation of all extensor muscles of the upper limb, as well as providing sensory innervation to the skin of the posterior arm, forearm, and part of the hand.

Spinal nerve rootsC₅–Th₁

OriginPosterior cord (*fasciculus posterior*)

Main functionInnervation of extensor muscles

BifurcationLevel of the lateral epicondyle of the humerus

Origin and Topography of the Main Trunk

The radial nerve is formed by fibers from spinal nerves C₅–Th₁ and is the continuation of the posterior cord of the brachial plexus (fasciculus posterior).

As it courses down the arm, the nerve travels through the humeromuscular canal (canalis humeromuscularis), after which it heads toward the cubital fossa (fossa cubitalis). Along this path, muscular and cutaneous branches arise from the main trunk to supply the triceps brachii muscle and the skin of the posterior arm.

Branches Prior to Division (At the Arm Level)

Several important branches arise from the main trunk of the nervus radialis in the arm:

Muscular branches (rr. musculares). These supply the long, lateral, and medial heads of the triceps brachii muscle (m. triceps brachii), as well as the anconeus muscle (m. anconeus).
Posterior cutaneous nerve of the arm (n. cutaneus brachii posterior). Provides sensory innervation to the skin on the posterior aspect of the arm.
Inferior lateral cutaneous nerve of the arm (n. cutaneus brachii lateralis inferior). Innervates the skin of the lower lateral part of the arm.
Posterior cutaneous nerve of the forearm (n. cutaneus antebrachii posterior). Provides sensation to the skin of the posterior forearm.

Terminal Branches: Superficial and Deep

Upon reaching the level of the lateral epicondyle of the humerus, the radial nerve divides into two major terminal branches:

Superficial branch (r. superficialis n. radialis). This is an exclusively sensory branch. It runs down the forearm deep to the brachioradialis muscle (m. brachioradialis). Descending onto the hand, this branch innervates the skin of the dorsal radial side of the hand, the thumb, and partially the proximal phalanges of digits II and III.
Deep branch (r. profundus n. radialis), also known as the posterior interosseous nerve (n. interosseus posterior). This branch is predominantly motor and passes to the posterior compartment of the forearm to innervate the distal group of extensors.

Innervation Zones of the Deep Branch

The deep branch of the radial nerve performs a substantial amount of work innervating the forearm muscles and upper limb joints.

Muscular innervation includes the following muscles:

Supinator muscle (m. supinator);
Extensor digitorum (m. extensor digitorum);
Extensor digiti minimi (m. extensor digiti minimi);
Extensor carpi ulnaris (m. extensor carpi ulnaris);
Abductor pollicis longus (m. abductor pollicis longus);
Extensor pollicis brevis (m. extensor pollicis brevis);
Extensor pollicis longus (m. extensor pollicis longus).

In addition to muscles, the deep branch gives off articular branches to the elbow joint (articulatio cubiti), radiocarpal joint (articulatio radiocarpalis), and metacarpophalangeal joints (articulationes metacarpophalangeae).

Frequently asked questions

Which muscles are innervated by the muscular branches of the radial nerve before it divides into terminal branches?

Before dividing into terminal branches, the muscular branches of the radial nerve innervate:

Triceps brachii muscle (m. triceps brachii) — long, lateral, and medial heads.
Anconeus muscle (m. anconeus).

Which forearm muscles are innervated by the deep branch of the radial nerve?

The deep branch of the radial nerve (r. profundus n. radialis) innervates several muscles of the posterior forearm compartment. These include:

Supinator (m. supinator).
Extensor digitorum (m. extensor digitorum).
Extensor digiti minimi (m. extensor digiti minimi).
Extensor carpi ulnaris (m. extensor carpi ulnaris).
Abductor pollicis longus (m. abductor pollicis longus).
Extensor pollicis brevis (m. extensor pollicis brevis).
Extensor pollicis longus (m. extensor pollicis longus).

Through which anatomical canal does the deep branch of the radial nerve enter the posterior compartment of the forearm?

The deep branch of the radial nerve enters the posterior compartment of the forearm through the supinator canal (canalis supinatorius). This canal is located between the superficial and deep parts of the supinator muscle (m. supinator). Passing through it, the nerve, accompanied by the muscle, wraps around the neck of the radius and enters the posterior fascial bed to innervate the muscles of the posterior forearm.

Where does the radial nerve divide into its superficial and deep branches?

The radial nerve divides into superficial and deep branches at the level of the lateral epicondyle of the humerus.

From which cord of the brachial plexus does the radial nerve arise?

The radial nerve originates from the posterior cord of the brachial plexus (fasciculus posterior).

Which digits of the hand does the superficial branch of the radial nerve innervate?

The superficial branch innervates the skin of the thumb and partially the proximal phalanges of digits II and III on the dorsal surface of the hand.

Go deeper

Topography of the humeromuscular canal (canalis humeromuscularis)
Boundaries and contents of the cubital fossa (fossa cubitalis)
Muscles of the posterior compartment of the forearm
Anatomy of the posterior cord of the brachial plexus
Sensory zones of the dorsum of the hand and innervation overlap