Figure. Magnetic resonance imaging of the left leg.
A 33-year-old man presents with pain and numbness in the lateral expect of his left lower leg that have been present for several months. The symptoms stop at the ankle level, and the pain is made worse with squatting or bending the knee. Previous radiographs of the knee and leg were unremarkable. Electromyography (EMG) conducted recently showed common peroneal neuropathy. Magnetic resonance imaging (MRI; Figure) depict neither evidence of a cyst impinging on the common peroneal nerve nor evidence of nerve root tumor. MRI of the lumbar spine is unremarkable.
Which of the following is the best treatment option for this patient’s common peroneal neuropathy?
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The common peroneal nerve courses superficial to the lateral border of the fibula and 1 cm to 2 cm distal to the head of the fibula before it goes through an intermuscular septum. Once the common peroneal nerve passes through the septum, it courses through the fibular tunnel, which comprises the soleus muscle laterally and a fibrous arch medially. In some patients, this arch is thick and unyielding, which can cause nerve irritation. Common peroneal nerve entrapment occurs when the nerve is compressed under this arch in the area where it bifurcates into the superficial and deep branches. Dynamic compression of the nerve within this arch can also occur when the knee is bent; sitting in a cross-legged position often worsens symptoms. Compression of the nerve can cause loss of sensation and pain along the posterior lateral leg, as well as foot drop.1,2
Other sources of neuropathy — such as lumbar spine pathology, cyst from the knee compressing the nerve, and a nerve root tumor — must be ruled out before common peroneal nerve entrapment can be diagnosed. EMG and MRI of the spine and knee are usually performed to rule out these other causes. Spontaneous recovery can frequently occur, but symptoms lasting longer than 6 months may require surgical decompression.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).
- Fabre T, Piton C, Andre D, Lasseur E, Durandeau A. Peroneal nerve entrapment. J Bone Joint Surg. 1998;80(1):47-53.
- Maalla R, Youssef M, Ben Iassoued N, Sebai MA, Essadam SH. Peroneal nerve entrapment at the fibular head: outcomes of neurolysis. Orthop Traumatol Surg Res. 2013;99(6):719-722.