Posterior interosseous nerve compression at the elbow

By Dr Maxime Cievet-Bonfils, hand, wrist and elbow surgeon in Lyon, France · Updated 2026-10-16 · Version française

Posterior interosseous nerve compression is the pinching of a branch of the radial nerve just below the elbow, most often under the arcade of Frohse, where it enters the supinator muscle. It causes pain on the outer side of the forearm, a few centimetres below the elbow, often confused with tennis elbow. Treatment starts with rest and rehabilitation; if this fails, an operation releases the nerve.

What is the posterior interosseous nerve?

The radial nerve runs down the arm and divides into two branches at the elbow. The deep branch, called the posterior interosseous nerve, passes under a fibrous arch, the arcade of Frohse, then through the supinator muscle to control the muscles that straighten the wrist and fingers.

At this level, the nerve can be compressed by the arcade of Frohse, the edge of the supinator muscle, blood vessels crossing it or, more rarely, a lump (cyst, lipoma). Repeated forearm rotation and forceful gripping make the symptoms worse.

There are two forms:

• the painful form (radial tunnel syndrome), by far the most common: pain without clear loss of strength
• the paralytic form, which is rare: the fingers no longer straighten fully, while feeling in the hand is normal

What are the symptoms?

• Pain on the outer side of the forearm, 4 to 5 cm below the elbow, sometimes spreading towards the wrist
• Pain when rotating the forearm, gripping objects or straightening the middle finger against resistance
• A feeling of fatigue or weakness in the forearm
• In the paralytic form: difficulty lifting the fingers, especially the thumb

The compression can coexist with tennis elbow, which explains some pain that persists despite well-conducted treatment for tennis elbow.

How is it diagnosed?

Diagnosis is mainly clinical: the surgeon looks for precise tenderness on pressure along the course of the nerve, lower down than the epicondyle, and for pain on supination (palm up) against resistance. The surgeon distinguishes this compression from tennis elbow or radial head micro-instability, with which it can be associated.

• Ultrasound shows the nerve and looks for a local cause of compression
• The electromyogram (EMG, nerve conduction study) is often normal in the painful form; it is essential in the paralytic form
• An MRI is requested if a lump is suspected
• An anaesthetic test is always carried out: a small amount of local anaesthetic is injected, under ultrasound guidance, next to the nerve at the arcade of Frohse. If the pain disappears for a few hours, the nerve is indeed the cause

What are the non-surgical treatments?

• Reducing triggering movements, especially forceful rotation
• Rehabilitation with a hand therapist (physiotherapist)
• Resting wrist splint during painful phases
• Painkillers for short periods

Corticosteroid injections are not used.

When is surgery needed?

The operation is offered when pain persists and is troublesome despite several months of well-conducted treatment. In the paralytic form, it is considered earlier, especially if a cause of compression is identified or if recovery does not begin.

How is the operation performed?

Through an incision on the outer side of the forearm, below the elbow, the surgeon opens the arcade of Frohse and releases the nerve along its course through the supinator muscle, treating any other cause of compression. If tennis elbow or instability is also present, it can be treated at the same time.

The operation is done as a day case, under regional anaesthesia of the arm.

After the operation

• The elbow and fingers are moved early for gentle movements
• A dressing is kept on for about two weeks
• Return to strenuous effort and repetitive movements is gradual
• Pain generally decreases over several weeks; in the paralytic form, recovery of strength can take several months

Complications are rare (haematoma, infection, tender scar, complex regional pain syndrome) and are explained to you in consultation.

Frequently asked questions

How can it be told apart from tennis elbow?

The pain of tennis elbow is centred on the bony bump on the outer side of the elbow; the pain of posterior interosseous nerve compression lies a few centimetres lower, along the course of the nerve. The two can coexist, and clinical examination makes it possible to tell which is which.

Why is my electromyogram normal?

In the painful form, the nerve is irritated without being damaged enough to change the electromyogram. A normal test therefore does not rule out the diagnosis, which is based on clinical examination.

Will I lose feeling after the operation?

No. The posterior interosseous nerve mainly controls muscles; the operation consists of releasing it, not cutting it.

This page provides general information. It does not replace a consultation: every situation is different.