When surrounding structures put pressure on a nerve, it’s referred to as a pinched nerve. It causes symptoms in the part of the body that’s supplied by that nerve.
This article describes the causes and treatment of a pinched nerve in your knee.
A nerve becomes pinched when too much pressure is placed on it by the bone, tissue, or other structures around it.
This injures the nerve so it can’t function properly.
Although it’s most commonly associated with the nerves in your back, almost any nerve in your body can become pinched. Doctors call it nerve compression or entrapment.
There’s only one nerve going through your knee that’s at risk of being compressed. It’s a branch of your sciatic nerve called the peroneal nerve.
This nerve goes around the outside of your knee before traveling down the outside of your lower leg.
At the bottom of your knee, it lies between the bone and skin, which makes it vulnerable to compression by anything that puts pressure on the outside of your knee.
Traumatic injuries can lead to pressure on the nerve from inside your knee.
Common causes of a pinched nerve in your knee include:
- Crossing your legs. Compression by the opposite knee while you cross your legs is the most common cause.
- Squatting for long periods of time. This position put pressure on the side of your knee.
- Bone fracture. A fracture of the larger lower leg bone (tibia) or occasionally the smaller bone (fibula) near your knee can entrap the nerve.
- Knee ligament injury. The nerve can be pinched due to bleeding or inflammation when your ligament is injured.
- Lower leg cast. The top of the cast can press on the nerve.
- Knee brace. A tight or rigid brace can compress the nerve.
- Knee-high boots. When the top of a boot lands right below the knee, a pinched nerve can develop.
- Gynecologic or abdominal surgery. The equipment used to keep your legs rotated outward and knees flexed for most gynecologic and some abdominal surgeries can compress the nerve.
- Prolonged bed rest. Your legs tend to rotate outward and your knees flex while lying down, and the bed can put pressure on the nerve in this position.
- Thigh-high compression stockings. Designed to maintain pressure on your legs, these stockings can compress the nerve.
- Tumors or cysts. These can cause pressure when they’re located in or around the nerve.
- Complication of knee surgery. Rarely, the nerve is inadvertently pinched during knee replacement surgery or an arthroscopic procedure.
The peroneal nerve supplies both sensation and movement to the outside of your lower leg and the top of your foot. When it’s compressed, it becomes inflamed, which causes the symptoms of a pinched nerve.
Usually only the lining, or myelin, around the nerve is injured. When the nerve itself is also damaged, the symptoms are the same but more severe.
Weakness that limits your ability to lift your foot toward your leg, known as dorsiflexion, is often considered the most bothersome symptom. This causes your foot to drag when you walk.
Your ability to turn your foot outward and extend your big toe are also affected.
Other symptoms of a pinched peroneal nerve are felt on the outside of your lower leg and on the top of your foot. These include:
If you’ve had a pinched nerve for two or more weeks, the muscles supplied by the nerve can begin to waste away.
Your symptoms may be intermittent or continuous depending on what’s pushing on the nerve.
The other common cause of these symptoms is a pinched nerve in your lumbar spine. When this is the cause, you’ll also have pain in your lower back or the back and outside of your thigh.
Your doctor will take your medical history and perform an exam to try to make a diagnosis and determine the cause.
The nerve in your knee can be felt as it travels around the top of your tibia, so your doctor may tap on it. If you feel a shooting pain down your leg, you probably have a pinched peroneal nerve.
Tests your doctor may order include:
- Knee X-ray: shows any bone fractures or masses
- Knee MRI: can confirm the diagnosis and show masses within the nerve and details of fractures of other problems in your bones
- Electromyogram (EMG): tests electrical activity in your muscles
- Nerve conduction test: tests the speed of signals in the nerve
The problem or activity that’s causing the pinched nerve should be treated or corrected first.
Treatment is aimed at reducing pain and improving mobility.
Over-the-counter pain medication
Any medication that reduces inflammation can improve your symptoms, such as anti-inflammatories like ibuprofen and naproxen.
Heat or ice
Applying either heat or ice for 15 to 20 minutes at a time can give some relief from the symptoms.
If you’ve lost sensation, you have to be careful you don’t get frostbite or a burn on your skin. An ice pack can make your symptoms worse if it puts too much pressure on the nerve.
A corticosteroid injection can reduce the inflammation, which reduces the pressure on your nerve.
If your gait is affected because you can’t bend your foot, an orthotic boot can help. This is a support that keeps your foot in a neutral position so you can walk normally.
Your doctor can perform surgery to correct a fracture, tumor, or other invasive problem causing a pinched nerve.
If conservative treatment doesn’t work, a procedure called peroneal nerve decompression can done to remove the pressure on your nerve.
Your nerve can be permanently damaged if it’s pinched for a long time. If that happens, it can’t be fixed with surgery. Physical therapy can be helpful for strengthening and gait training
Usually a pinched peroneal nerve will get better on its own within days to weeks once you stop the behavior or fix the condition that’s causing it.
If surgery is needed, your symptoms should disappear immediately, but it takes about four months to recover from surgery.
Things you can do to prevent a pinched peroneal nerve include:
- Avoid behaviors and activities that cause it such as crossing your legs, frequent squatting, and wearing knee-high boots.
- Tell your doctor if a cast or brace feels tight or is causing numbness or pain in your leg.
- Use devices that softly hold your ankles to prevent leg rotation during prolonged bed rest.
- Reposition yourself frequently during prolonged bed rest to avoid continuous pressure on the side of your knee.
The peroneal nerve that runs along the outside of your knee can become pinched when it’s compressed. Crossing your legs is the most common cause but anything outside or inside your knee that puts pressure on the nerve can do it.
A pinched nerve in the knee usually heals itself when the cause is removed, but surgery is sometimes needed to relieve the pressure.