The radial nerve is a major branch of the brachial plexus. It travels from the shoulder region down the back of the arm, wraps around the humerus and continues into the forearm, where it helps straighten the wrist and fingers.

Location

Continues from the posterior cord of the brachial plexus
Leaves the armpit region with the deep artery of the arm
Spirals closely around the back of the humeral shaft
Crosses toward the outer side of the elbow
Divides into branches that supply movement and sensation in the forearm and hand

Function

Powers the triceps to straighten the elbow
Powers muscles that lift the wrist and straighten the fingers
Helps position the forearm for grip and hand use
Carries sensation from parts of the back of the arm, forearm and hand

Why It Matters at the Shoulder and Upper Arm

The radial nerve begins at the shoulder, but one of its most vulnerable points is farther down, where it lies close to the humeral shaft. A mid-shaft humerus fracture can injure the nerve and cause difficulty lifting the wrist or fingers—a pattern often called wrist drop.

Weakness after an upper-arm injury should be assessed rather than blamed on pain alone.

Common Problems

Radial nerve injury with a humeral shaft fracture
Compression from prolonged pressure on the upper arm
Posterior cord or brachial plexus injury
Entrapment of a branch near the elbow or forearm

Symptoms That May Need Assessment

New difficulty straightening the wrist, fingers or elbow
Numbness on the back of the hand near the thumb
Weakness after an upper-arm fracture, dislocation or deep cut
Progressive weakness or loss of coordination

Sudden major weakness, severe trauma or signs of reduced circulation require prompt medical assessment.

Brachial plexus — the network where the radial nerve begins
Proximal humerus — the upper-arm bone the nerve travels around farther down its shaft
Referred neck and arm symptoms — another possible source of arm symptoms

References

StatPearls. "Anatomy, Shoulder and Upper Limb, Radial Nerve." https://www.ncbi.nlm.nih.gov/books/NBK534840/
StatPearls. "Radial Nerve Injury." https://www.ncbi.nlm.nih.gov/books/NBK537304/

Radial Nerve