Overview of Peroneal Nerve Entrapment
Irritation and entrapment of the common peroneal nerve where it crosses the fibular head can be due to scar tissue, trauma, or other causes. One of the first things to do in the assessment of possible common peroneal nerve entrapment is to verify that the irritation in the common peroneal nerve at this location is not due to a lumbar spine cause, such as a herniated disk or spinal stenosis, and is truly localized to the common peroneal nerve itself.
Once it has been determined that the irritation of the common peroneal nerve is located at the fibular neck, one most commonly confirms this diagnosis on physical exam. The common peroneal nerve can be palpated where it crosses the lateral aspect of the fibula about 2 centimeters distal to the fibular head. In addition, about 3 to 4 cm proximal to this, it courses out from under the undersurface of the long head of the biceps femoris. Therefore, the nerve can usually be palpated in most patients by the examiner rolling the nerve under one’s fingers, where it crosses the lateral aspect of the fibular shaft.
When one elicits a positive response to palpation or rolling of the common peroneal nerve at this location, one would anticipate that it would reproduce a “zinging”-type sensation down the lateral aspect of the leg and over the dorsum of the foot (a positive Tinel’s sign). In most circumstances, there is no significant motor weakness, unless there has been a knee ligament dislocation or an injury to the posterolateral knee structures. In any event, one should perform a thorough physical exam to validate that the main motor structures innervated by the common peroneal nerve are still intact. This includes ankle dorsiflexion, EHL strength, total extension, and foot eversion strength.
As part of the evaluation for common peroneal irritation, is important to verify that the pain in this area is not due to other pathology such as biceps bursitis, tendinopathy or a sprain of the long head of the biceps at its attachment on the lateral aspect of the fibular head, a snapping biceps femoris tendon, a cyst of the proximal tibiofibular joint, or a lateral meniscus tear.
While we do recommend the use of an EMG/NCV as part of the workup to validate that the nerve irritation is coming from entrapment at the fibular head/neck region, it is actually very rare that these findings are positive on these studies. In effect, the main use of these neurology studies is to validate that the nerve irritation is not coming from a herniated disk or other spinal cause.