Overview

Peroneal nerve injury is the most common peripheral neuropathy in the lower extremities and the third most common neuropathy. The peroneal nerve, also referred to as the fibular nerve, descends below the knee with two subdivisions: the superficial and deep peroneal nerves play a role in controlling movement and sensation of the lower leg. Because the peroneal nerve is close to the knee joint, it is more vulnerable to injury and damage. There are different kinds of damage to this nerve which can lead to peroneal nerve injury varying in severity. Symptoms of peroneal nerve injury can range from numbness to a ‘foot drop’, a way of walking caused by an inability to flex the foot upwards at the ankle.

Understanding the causes of peroneal nerve injury is vital for prevention and treatment. In this article, we will highlight the main causes of peroneal nerve injury: trauma, compression-related injury and medical conditions, and how peroneal nerve injuries can be diagnosed and managed.

What is the peroneal nerve?

The peroneal nerve is a major nerve descending into the legs, which branches out from the sciatic nerve and divides into the superficial peroneal nerve near the fibular neck, and the deep peroneal nerve, terminating in the first and second toes. The superficial peroneal nerve controls the movement of turning the ankle outwards, and the deep peroneal nerve is responsible for controlling dorsiflexion (the ability to point the toes downwards).

Peroneal nerve injury is characterised as peroneal nerve palsy, which describes dysfunction or paralysis of the nerve, resulting in the symptoms typically associated with peroneal nerve injury, including:

• Foot drop (being unable to lift the foot up)
• Numbness
• Weakness in foot
• Gait abnormality- deviation from normal walking patterns

Trauma-related causes of peroneal nerve injury

Trauma is the most common cause of peroneal nerve injury. The peroneal nerve is susceptible to direct blows, fractures and external compression because it wraps around the fibular head of the knee and is unprotected by muscle or fat. Trauma to the nerve can be caused by several external forces.¹

Direct trauma

Trauma and injuries to the knee joint can lead to knee dislocations and fibular fractures, ultimately leading to peroneal nerve damage. The fibular head is an exposed area where the nerve is close to the bone, which increases the risk of injury. Straightforward impact and cuts cause direct trauma to the peroneal nerve.²

Medical and surgical procedures

Surgeries and medical procedures can cause peroneal nerve injuries due to the proximity of surgical instruments to the nerve, causing trauma to the nerve. These can include:

• Total knee arthroplasty (knee replacement surgery)¹
• Epidural anaesthesia during childbirth
• Tibial osteotomy (removal of the bone to straighten out the leg)²
• Knee arthrodesis (a surgical procedure that fuses the bones of the knee joint)
• Knee extensor realignment (procedure to correct the alignment of the knee’s extensor apparatus)
• Arthroscopic meniscal repair (minimally invasive surgeries to repair knee cartilage)
• Treatment of knee flexion contracture (treating chronic knee bending where the knee joint is stuck in a bent position preventing full extension)³

Compression-related causes of peroneal nerve injury

Compression injuries can occur when external pressure is applied to the peroneal nerve over time, causing damage to the nerve and disrupting function. These injuries can result from mechanical compression, prolonged immobility, or repetitive activities.

External compression can include:

• Wearing tight plaster casts or splints
• Consistent leg crossing
• Prolonged bed rest, particularly in comatose patients
• Positioning during surgery
• Prolonged leg crossing¹

Lifestyle factors and risk factors

Behavioural causes of peroneal nerve injury include a prolonged crossed-leg posture, or repetitive stretching from squatting could cause injury. Peroneal nerve injury can be more common for those of a particular occupation, such as athletes who are more susceptible to injury during sports, and for those whose jobs require extensive kneeling and squatting, leading to persistent compression of the nerve.²

Medical conditions

Several underlying medical conditions can predispose individuals to peroneal nerve injury and cause compression or damage to the peroneal nerve.

Systemic diseases like diabetes often cause complications such as high blood sugar, high triglyceride and cholesterol levels and reduced blood flow, which can degrade nerves and cause damage. Autoimmune diseases can also cause nerve injury, including chronic inflammatory demyelinating polyradiculoneuropathy. Individuals who have an incredibly low body mass index, eg, those suffering from anorexia nervosa, can be more susceptible to compressive injury of the nerve due to fat loss.^4,1

Lesions and tumours can also cause nerve damage. The most common lesions associated with peroneal nerve injuries are intraneural ganglion cysts, which are a build-up of fluid that forms near the outer layer of a nerve and can cause compression neuropathy.  Schwannomas are the most frequent non-cancerous tumours to arise from peripheral nerves, including in the peroneal nerves, and other tumours can also cause compression to the nerve.^1,5,3

Diagnosis of peroneal nerve injury

A clinical evaluation by a medical professional is required for diagnosing peroneal nerve injuries. This is typically done by looking at:

Assessing patient history, including a physical examination of the lower leg and foot. This could also involve using CT scans, MRIs, ultrasounds and X-rays.

Electrodiagnostic studies, including electromyography and nerve conduction velocity can be used to test the functionality of the superficial and deep peroneal nerve, as well as pinpoint the exact location of the damage. Electrodiagnostic studies are particularly useful in patients who present with new peroneal nerve injury symptoms without a traumatic event occurring to identify the cause, which could be nerve compression, a systemic condition or another underlying issue.¹

Treatment of peroneal nerve injury

Peroneal nerve injury can be treated surgically and non-surgically.

Non-surgical treatment

Physical therapy can include stretching, mobilisation, proprioceptive training, and ankle bracing, all to improve motor function in the affected leg(s). Ultrasound-guided pulsed radiofrequency therapy could also be useful in specific cases.^1,6

An ankle foot orthotic is a plastic splint worn over the foot which can help with treating foot drop and improving ankle stability.¹

Surgical treatment

Surgery is considered in severe cases of peroneal nerve injury; those that have worsening symptoms, no improvement after 3 months, or open nerve cuts, in which surgery should occur within 72 hours of the traumatic event. Surgeries that can treat peroneal nerve injury include:

• Nerve decompression surgery conducted at the fibular head can help with compressive neuropathy
• Muscle transfer surgery could be considered in the case of a permanent foot drop
• Botulinum toxin injections can be considered in cases of spastic (irregular) foot drop

Differential diagnosis of the peroneal nerve injury

Foot drop is most commonly caused by peroneal nerve injury, but can also result from other conditions as well, but can also result from other conditions including lumbar radiculopathy and multiple system atrophy.¹

FAQs

How many people are affected by peroneal nerve injury?

Peroneal nerve injury is the most common neuropathy of the lower extremities. Many patients have developed a peroneal nerve injury after surgery. Up to 40% of patients have been found to have a peroneal nerve injury after knee dislocation caused by trauma.

Who is more likely to develop a peroneal nerve injury?

Anyone can be susceptible to a peroneal nerve injury, though injuries to the knee are becoming increasingly common in teenagers. Typically, peroneal nerve injuries occur due to injury or trauma, with lifestyle factors being the second most common cause. 

How long does peroneal nerve damage recovery take?

Recovery can vary depending on the severity of the nerve damage. It can range from weeks to months.

Can peroneal nerve injuries heal on their own?

Less severe nerve injuries may recover with physical therapy and ankle braces, though more severe cases could require surgery.

How can peroneal nerve injury be prevented?

Avoid prolonged pressure on the outer knee, for example by not crossing the legs for an extended amount of time or squatting for too long, and in medical settings, make sure patients are moved around when they are immobile or unable to move by themselves.¹

Summary

Peroneal nerve injuries are one of the most common nerve injuries that can occur, with multiple causes responsible, including trauma, consistent nerve compression and medical conditions. Understanding what can cause peroneal nerve injuries is essential for early intervention and prevention, especially with external compression and nerve compression caused by lifestyle and which could be prevented entirely. Accurate and timely diagnosis and the appropriate treatment can greatly improve outcomes for patients.