Common peroneal nerve entrapment: pain, numbness and when to release the nerve

An ache at the outside of your knee. Tingling down the outer shin and across the top of your foot. Maybe your toes catch on a step. If a doctor has said “common peroneal nerve,” here is what that means and how surgery can help.

What is common peroneal nerve entrapment?

The common peroneal nerve, also called the common fibular nerve, is a branch of the sciatic nerve. It controls the muscles that lift your foot and toes and gives feeling to the outer lower leg and top of the foot.^[2] Just below the knee it wraps around the fibula, the thin outer bone of the leg. There, close to the skin, the bony bump of the fibula is the most common place for it to be squeezed.^[1]

Entrapment means the nerve is trapped and pressed at that spot. Palsy means the nerve has lost some of its ability to move muscles or carry feeling.^[2]

What does common peroneal nerve pain feel like?

Common signs include numbness or tingling on the top of the foot or outer leg, weakness lifting the foot, toes that drag and a slapping step.^[2] About half the people in one surgical series came in with pain.^[5]

For some people it is worse when walking. In seven people whose symptoms came on with walking, pressure on the nerve rose more than tenfold when the foot pointed down. It fell step by step as the surgeon released the tight tissue around it.^[6]

Why does the nerve get trapped?

• Outside pressure. Crossing the legs, tall boots, a tight cast, or lying in one position during deep sleep.^[2]
• Injury or surgery. A knee injury, a broken fibula, or knee surgery.^[2] In one series of 30 people, 14 followed an injury and 12 followed an operation.^[5]
• A cyst inside the nerve. An intraneural ganglion is a fluid-filled cyst that grows inside the nerve. Pain, foot drop and swelling are common signs.^[7]
• Tight tissue with no clear trigger. Some cases have no outside cause, and the nerve is trapped by tight bands near the fibula.^[8,6]
• Higher risk. People who are very thin or have diabetes or certain nerve conditions are more prone to it.^[2]

How do you treat common peroneal nerve dysfunction?

Start by removing the pressure. Stop crossing your legs, change the boot or loosen the cast, and pad the knee. A brace can hold the foot up while you walk. Medicines can help nerve pain.^[2] Many entrapments settle with these steps.^[1]

These steps are the bridge, not always the answer. Surgery may be needed if the problem doesn’t go away, if you have trouble moving the foot, or if tests show damage to the nerve fibers.^[2] When entrapment doesn’t respond, one review says surgery is often required.^[1]

Does decompression surgery help pain and numbness?

Yes, for many people. Decompression, also called neurolysis, opens the tight tissue around the nerve near the fibula so the nerve is no longer squeezed. Dr. Efe Ozturk, a double board certified Foot and Ankle Surgeon and podiatrist, evaluates peroneal nerve entrapment and can talk with you about whether release is right for you. Our nerve decompression page explains how nerve release works.

• Pain. Pain improved in 84% of 31 people in one series and 31 of 37 in another.^[3,9]
• Strength. Strength improved in 83% of 48 people with weakness, and in 24 of 26 in a third series.^[3,5]
• Feeling. Numbness is slower to recover. Sensation improved in 49% in one series. In another, 19 of 42 people had normal feeling again.^[3,9]
• Overall. In 15 people, 12 had an excellent or good result. Function returned in an average of 2.5 months.^[8]

Results were favorable across different symptoms in a combined analysis of 136 operations, and older age did not lower them.^[4] Many people with this entrapment also have a pinched L5 nerve in the back. In one study, those people did as well after knee-level release as those without back trouble.^[10] Complications were rare in a pooled review of 368 people.^[11]

Our main practice explains foot nerve pain (external site) and its causes.

Why does timing matter?

The sooner a trapped nerve is freed, the better it tends to recover.

• Symptoms lasting longer than 12 months before surgery were linked to unfavorable results. People with tingling or numbness may do better with surgery within six months of onset.^[4]
• In one series, waiting more than about 506 days lowered the chance of normal feeling returning.^[9]
• One surgical team prefers to operate at three to four months if symptoms persist, even when they are only sensory. They found recovery was faster after surgery than with rehabilitation alone.^[8]
• In severe weakness with no clear cause, the authors of one study advise considering early surgery. The one person who didn’t improve had waited the longest.^[12]

What if a cyst is pressing on the nerve?

For an intraneural ganglion, surgery to remove it is recommended, especially when it weakens the foot.^[7] In eight people followed for an average of more than nine years, all had significant pain relief, and median foot strength rose from 0 to full strength.^[13] Across six studies of 128 people, function and symptoms improved after surgery. Recurrences ranged from 0% to 25%, and most were outside the nerve.^[7]

How is it diagnosed?

Your exam guides the plan. We test strength in the muscles that lift and turn the foot, map any numbness, and check the knee and back. Tapping over the nerve isn’t always positive; only 12 of 30 people in one series had that sign.^[5] Nerve studies, EMG and diagnostic nerve blocks help confirm the problem.^[1] Ultrasound and MRI both show good accuracy.^[14] These tests are arranged with another specialist. See back or foot: finding the source of nerve pain and common peroneal nerve compression.

What are the limits?

Surgery doesn’t help everyone, and numbness may not fully recover.^[3] Diabetes was linked to less favorable results, and smoking showed a trend toward worse results.^[4] A body mass index (BMI) above about 29 lowered the odds of normal feeling returning.^[9] The share of good results after neurolysis varied widely between studies, from 40% to all patients. Most studies are case series, and none compared surgery directly with non-surgical care.^[14] Risks include infection, wound problems and bleeding, and one death from sepsis was reported among the 368 people.^[11]

Common questions

Does common peroneal nerve injury cause foot drop?

Yes. Foot drop, trouble lifting the front of the foot, is one of its main signs.^[2] See can drop foot be fixed?

Can common peroneal nerve entrapment heal on its own?

Many cases improve once the pressure is gone.^[1] If yours hasn’t improved within a few months, ask about surgery, because results fall with delay.^[4,8]

What is common peroneal nerve palsy?

It means the nerve isn’t working fully, causing weakness, numbness or both in the leg and foot.^[2]

When to see a specialist

See us for pain at the outside of the knee, numbness on the top of the foot, or any new trouble lifting the foot. We see patients in Lyndhurst, Paramus and Millburn. Please call our office at 908-215-5953 to inquire about your insurance.