Superficial Peroneal Nerve Entrapment


The superficial peroneal nerve travels in the lateral compartment and supplies the peroneus longus and brevis muscles. In most individuals, the superficial peroneal nerve pierces the deep fascia and emerges into the subcutaneous fat at approximately the level of the middle and lower third of the leg and at an average of about 10-15 cm above the tip of the lateral malleolus.41 At an average of 4-6 cm proximal to the ankle joint, it divides into a large (2.9 mm) medial dorsal cutaneous nerve and a smaller (2 mm), more laterally located intermediate dorsal cutaneous nerve.

In 28% of patients, the superficial peroneal nerve branches more proximally. In these cases, the medial dorsal cutaneous branch usually follows the more common track of the superficial peroneal nerve and emerges into the subcutaneous tissues in the distal lateral leg. The intermediate dorsal cutaneous nerve penetrates the crural fascia more distally, either anterior or posterior to the fibula and at an average of 4-6 cm proximal to the ankle joint. At the level of the malleoli, in most patients, the medial dorsal cutaneous nerve is located at approximately half of the distance from the lateral malleolus to the medial malleolus, and the intermediate dorsal cutaneous nerve is at approximately one third of the distance.

The medial dorsal cutaneous nerve supplies the skin of the dorsomedial aspect of the ankle, the medial aspect of the hallux, and the second and third digits (except for the first webspace). The intermediate dorsal cutaneous nerve supplies the skin on the dorsolateral part of the ankle and gives off dorsal digital nerves for the third, fourth, and fifth toes.

Accessory branches of the superficial peroneal nerve have been reported to cross over the lateral malleolus, where they have been entrapped by fascial bands. An accessory motor branch of the superficial peroneal nerve has also been found to innervate the EDB in some patients.42


Local trauma or compression is the most common underlying cause of entrapment of the superficial peroneal nerve. Repeated ankle sprains or the use over many years of certain positions, such as prolonged kneeling and squatting, can make certain individuals more prone to the development of symptoms. This tendency is thought to be due to recurrent stretch injury to the nerve. Perineural fibrosis of the superficial peroneal nerve at the level of the ankle following an inversion ankle sprain has been reported.43

This nerve is also at risk for direct injury by any procedure about the anterior ankle, including use of the anterolateral ankle arthroscopy portal. Chronic or exertional lateral compartment syndrome can also cause compression of the superficial peroneal nerve, particularly in athletes.

Nontraumatic causes of entrapment are commonly due to anatomical variations, such as fascial defects with or without muscle herniation about the lateral lower leg, where the nerve is entrapped as it emerges into the subcutaneous tissue, or a short peroneal tunnel proximally.


Although patients may present with numbness or paresthesia in the distribution of the nerve, and occasionally have pain about the lateral leg, the most typical presentation is vague pain over the dorsum of the foot. The pain can be chronic, present for several years, and associated with other foot and ankle symptoms, or the pain can be acute and associated with recent trauma or surgery about the ankle. Use of the anterolateral arthroscopy portal, specifically, puts this nerve at risk for direct or stretch injury, as do noninvasive traction methods with straps over the dorsum of the foot. About one quarter of patients have a history of previous or recurrent ankle sprains or trauma.

Typically, symptoms increase with activity, such as running, walking, or squatting; rest or the avoidance of a specific activity often relieves the symptoms. This tendency is particularly pronounced in athletes whose symptoms are suggestive of exertional or chronic anterolateral compartment syndrome.

Bony entrapment of the superficial peroneal nerve in the fracture callus has also been reported when fractures of the fibula heal with abundant callus.

Certain positions, such as crossing the leg over the opposite thigh, can induce symptoms, as can tight clothing, such as sock elastic over the lateral leg. Pain may occasionally occur at night. Occasionally, patients report a bulging mass in the leg.

Examination should include the entire course of the nerve, starting from the lower back and extending through the sciatic notch, proximal fibula, and lateral leg, where a muscle bulge due to a fascial defect may be palpated in some patients. Percussion along the superficial course of the nerve over the proximal fibula, lateral leg, or anterior ankle may result in a positive Tinel sign, with reproduction of radiating pain. Direct palpation with pressure on the site of entrapment may also induce or exacerbate symptoms. Repeating the examination after a particular activity that exacerbates symptoms may produce findings not present on the initial examination at rest.

In competitive athletes who have symptoms suggestive of exertional compartment syndrome, Styf describes 3 provocative tests for nerve compression at rest and again at rest but after exercise.44 In the first test, pressure is applied over the anterior intermuscular septum while the patient actively dorsiflexes the ankle. In the second test, the foot is passively plantarflexed and inverted at the ankle. In the third test, while the patient maintains the passive stretch, gentle percussion is applied over the course of the nerve.

In some cases of superficial peroneal nerve entrapment associated with direct or indirect trauma, patients may present with symptoms of reflex sympathetic dystrophy (RSD)/complex regional pain syndrome (CRPS), which creates a diagnostic and therapeutic challenge.

Infrequently, weakness of the dorsiflexors and everters of the foot may be seen with associated foot drop in more proximal entrapments of the superficial peroneal nerve.

Although rare, plain radiographs of the leg may reveal bony abnormalities that may contribute to or be the cause of entrapment. In cases of suspected proximal entrapment, knee radiographs may show abnormalities of the proximal fibula, such as exostoses, osteochondromas, and fracture callus. If necessary, a CT scan can provide more detailed information on the bony anatomy of the area, and an ultrasonogram can help to localize cystic masses that impinge on the nerve.

An MRI study is rarely necessary to obtain additional information.

Occasionally, in cases of exertional compartment syndrome, the measurement of the intramuscular pressure at rest after exercise may be helpful.

Injection of the nerve with lidocaine or bupivicaine (Marcaine) just above the site of involvement can be the most valuable diagnostic tool. The patient can define the extent of relief obtained from such an injection, which can be helpful in defining the zone of injury and expected relief from surgical release or excision.

The value of electrodiagnostic studies varies in the literature. Although in many cases findings from electrodiagnostic tests are normal because these dynamic syndromes frequently improve or resolve at rest, these tests may reveal an unrecordable evoked response or a prolonged distal latency of a segment of the nerve and help to better define the zone of compression. They also help in the evaluation of concomitant radiculopathy or peripheral neuropathy.


Nonoperative options include the use of NSAIDs combined with relative rest, physical therapy for strengthening of muscles in cases of associated weakness or recurrent ankle sprains, and elimination of predisposing or triggering factors. Aids, such as braces, can be used to avoid recurrent ankle sprains. In-shoe orthotic devices may be helpful in certain instances, such as the correction of a biomechanical malalignment in gait for patients with severe flatfoot or cavus foot.

At times, injection of steroids plus lidocaine near the site of involvement in the lower leg can reduce symptoms and serve as a diagnostic tool in confirming the zone of nerve compression. The use of antineuritic medication, such as gabapentin, can also be helpful in reducing or sometimes eliminating symptoms, particularly in cases associated with CRPS. In these cases, combination treatment with medication, physical therapy, and local and sympathetic nerve blocks may be required.

Surgical decompression may be indicated in cases refractory to nonoperative options. This can include release of the superficial peroneal nerve at the lateral leg for surgical decompression with partial or full fasciotomy. Some authors have also advocated fasciectomy in select cases. Neurolysis generally is not indicated, as it has not been shown to improve outcome.

Styf and Morberg reported that 80% of their patients were free from symptoms or satisfied with the result after decompression of the superficial peroneal nerve.45 Three of 14 patients had local fasciectomy as well.

Styf reported on fasciotomy and neurolysis to treat entrapment of the superficial peroneal nerve in 24 legs (21 patients).44 Nine patients were satisfied with the result, another 6 had improvement but were not satisfied because of residual limitation of athletic activity, 3 had unchanged conditions, and 1 had a worsened condition. Conduction velocity in the superficial peroneal nerve increased postoperatively, although the change was insignificant. In 5 patients, the nerve had an anomalous course, and in 11 patients, fascial defects were present over the lateral compartment. The author concluded that operative decompression of the superficial peroneal nerve produces cure or improvement in about 75% of cases, but that it is less effective in athletes than in others.

Sridhara and Izzo reported complete symptomatic relief after surgical decompression.46 Johnston and Howell reported dramatically relieved pain after release and anterior transposition of the nerve in patients who had had neuralgia after inversion ankle sprain.47

The surgical procedure to release the superficial peroneal nerve at the anterolateral leg involves determining and marking preoperatively the location of maximum tenderness and, if present, lateral muscle herniation. The procedure is performed using magnifying loupes and a tourniquet. A 5-cm longitudinal incision is made over the anterolateral leg approximately at the junction of the middle and distal third to encompass these 2 points.

A significantly more distal point of tenderness may suggest a more distal piercing of the intermediate dorsal cutaneous nerve through the fascia, in which case 2 separate incisions could be considered. A blunt subcutaneous dissection is made, and the nerve is found where it emerges through the fascia. A local fasciotomy is performed, releasing the nerve proximally and distally until it is completely free. A complete fasciotomy, as advocated by some authors, is considered in cases associated with chronic compartment syndrome. The resultant peroneal muscle weakness, however, may affect athletic performance.

In cases of painful neuromas or clearly abnormal nerves due to direct or indirect trauma to the nerve, surgical excision of the nerve can be performed at the site of neuroma. If several branches are involved, excision of the nerve at the anterolateral leg can be considered. Dellon and Aszmann reported excellent results in 9 of 11 patients who underwent resection of the nerve and translocation of the proximal nerve stump into the muscles of the anterolateral compartment, combined with fasciotomy of the anterolateral compartment.48

In cases of superficial peroneal nerve entrapment associated with other conditions, such as ankle instability, treatment of the associated conditions should also be planned.

Vague and diffuse symptoms can create a diagnostic and therapeutic challenge for the treatment of the entrapped superficial peroneal nerve. The use of multiple diagnostic modalities, including repeat examinations, selective injections, and electrodiagnostic studies, is required. Treatment of the underlying cause should be undertaken, as should release of the entrapped nerve and excision of existing neuromas.