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Radial Tunnel Syndrome

(Posterior Interosseous Nerve Syndrome)

By David R. Steinberg, MD, Associate Professor, Department of Orthopaedic Surgery, and Director, Hand and Upper Extremity Fellowship, Perelman School of Medicine at the University of Pennsylvania

Radial tunnel syndrome is a disorder resulting from compression (pinching) of a branch of the radial nerve in the forearm or back of the arm or at the elbow.

The radial tunnel is called a tunnel because it is a narrow area through which the radial nerve passes around the elbow and through the forearm to the hand. The tunnel is made of the surrounding muscles, tendons, and ligaments. Causes of compression of the radial nerve at the elbow include injury, ganglia, lipomas (noncancerous fatty tumors), bone tumors, and inflammation of the surrounding bursae (small fluid-filled sacs that can lie under a tendon) or muscles.

Compression of the radial nerve results in cutting, piercing, or stabbing pain affecting the top of the forearm and back of the hand and side of the elbow. Pain results when the person tries to straighten the wrist and fingers. There is no numbness because the radial nerve carries more fibers that control movement rather than sensation. In advanced cases, the muscles that straighten the thumb and fingers become weak.

Doctors base the diagnosis of radial tunnel syndrome on an examination.


  • A splint

To reduce pressure on the nerve, the person should wear a splint on the wrist and/or the elbow and avoid rotating the wrist and bending the arm at the elbow.

If the wrist becomes weak and tends to droop (wristdrop) or if symptoms are not relieved after 3 months of nonsurgical treatment, surgery may be needed to relieve pressure on the nerve.