Posterior Interosseous Nerve Impingement Syndrome
What is it: The posterior interosseous nerve is a branch of the radial nerve that can get entrapped in the proximal forearm under the fibrous arch of the supinator or the supinator muscle.
How does it present: The patient usually presents with lateral forearm or elbow pain exacerbated by activities that require repetitive supination/pronation. It may often be misdiagnosed as lateral epicondylitis.
Common exam findings: On exam, the patient may have a positive Tinel's with tapping or pressing over the region of the nerve, usually four fingerbreadths or eight cm distal to the lateral epicondylitis. You may find weakness with resisted extension of the middle finger.
Tests and treatment: Unfortunately, no specific tests are helpful in diagnosis. Electromyography (EMG) often does not confirm the diagnosis. Treatment is usually conservative with modification of activities, resting, and icing. Physical therapy may be helpful. In recalcitrant cases, surgical intervention may be indicated.