Peroneal nerve palsy is damage or compression of the common peroneal nerve, a major nerve that runs along the outside of your knee and controls movement and sensation in your lower leg and foot. The hallmark symptom is foot drop, where you lose the ability to lift the front of your foot off the ground. It’s one of the most common nerve injuries in the lower limb, and in many cases it’s caused by something as simple as prolonged pressure on the outside of the knee.
Where the Nerve Runs and Why It’s Vulnerable
The common peroneal nerve branches off the sciatic nerve near the back of your knee, then wraps around the top of the fibula, the thin bone on the outside of your lower leg. Right at this spot, called the fibular head, the nerve sits just beneath the skin with almost no padding of muscle or fat to protect it. That makes it unusually exposed to pressure from the outside world.
After wrapping around the fibular head, the nerve splits into two branches. The superficial branch controls the muscles that turn your foot outward (eversion) and provides sensation to the outer lower leg and the top of your foot. The deep branch controls the muscles that pull your foot upward (dorsiflexion) and extend your big toe, and it provides sensation to the small patch of skin between your first and second toes. When the common nerve is damaged before it splits, both branches can be affected at once.
What Causes It
The most frequent cause is external compression at the fibular head. Habitually crossing your legs puts steady pressure right on that vulnerable spot. Prolonged bed rest, especially lying with the outer knee pressed against a hard surface, can do the same thing. Tight casts, leg braces, or compression stockings that press against the upper outer leg are also common culprits.
Beyond compression, direct trauma to the knee area (fractures, dislocations, or surgical injuries) can stretch or sever the nerve. Significant weight loss removes the small amount of protective tissue around the fibular head, making the nerve easier to compress. Systemic conditions like diabetes make nerves more susceptible to damage from even mild pressure that a healthy nerve would tolerate. Less commonly, cysts or tumors near the knee joint can press on the nerve from the inside.
Symptoms and What They Feel Like
The defining symptom is foot drop. You’ll notice you can’t pull your foot up toward your shin, and the front of your foot slaps the ground when you walk. Many people instinctively compensate by lifting their knee higher than normal with each step, a pattern called a high steppage gait, to keep their toes from catching on the ground. Even with this adjustment, tripping on uneven surfaces or stairs becomes common.
You may also lose the ability to turn your foot outward. Numbness or tingling typically appears on the top of the foot, the outer part of the lower leg, and the web of skin between the first and second toes. The severity ranges widely. Some people have mild weakness they only notice during exercise, while others completely lose the ability to lift the foot.
How It Differs From a Spinal Problem
Foot drop can also come from a compressed nerve root in the lower back, specifically at the L5 level. Because the symptoms overlap significantly, telling the two apart matters for getting the right treatment. The key clinical test is foot inversion: trying to turn the sole of your foot inward. That movement is controlled by muscles supplied through the tibial nerve, not the peroneal nerve. If you can turn your foot inward normally but can’t lift it up, the problem is almost certainly at the peroneal nerve. If inversion is also weak, the issue is more likely in the spine.
How It’s Diagnosed
A physical exam often points to the diagnosis, but nerve conduction studies and electromyography (EMG) confirm it and reveal how severe the damage is. These tests send small electrical signals through the nerve and measure how quickly and strongly the signal travels.
There are two main types of nerve injury these tests can identify. In a demyelinating injury, the insulating coating around the nerve is damaged but the nerve fiber itself is intact. The electrical test shows the signal slowing dramatically as it passes the fibular head, with a speed drop of more than 10 meters per second compared to the nerve below the injury. In an axonal injury, the nerve fiber itself is damaged or destroyed. The test shows reduced signal strength throughout the nerve. Demyelinating injuries generally recover faster and more completely than axonal ones, so this distinction directly affects what you can expect.
Imaging like MRI or ultrasound may be ordered to look for structural causes such as cysts, tumors, or bone fragments pressing on the nerve.
Treatment Without Surgery
When peroneal nerve palsy is caused by compression and the nerve fiber itself is still intact, the first step is removing whatever was putting pressure on the nerve. That might mean stopping a leg-crossing habit, padding the outside of the knee during sleep, loosening a cast, or adjusting positioning during long periods in a wheelchair or hospital bed.
An ankle-foot orthosis (AFO) is the most important practical tool during recovery. This lightweight brace fits inside your shoe and holds your foot at a neutral angle so it doesn’t drag. Several types exist. A solid AFO locks the ankle completely, which works well for significant weakness. A posterior leaf spring AFO has a flexible design that acts like a spring, allowing slight movement at the ankle for a more natural walking feel. A hinged AFO permits controlled up-and-down ankle motion, making it easier to walk on uneven ground or climb stairs. Carbon fiber versions are thinner and lighter, and they store energy during each step to help with push-off. Your provider will match the type to your level of weakness and activity needs.
Physical therapy focuses on strengthening the weakened muscles, maintaining range of motion in the ankle so it doesn’t stiffen, and retraining your gait pattern. Even while waiting for the nerve to recover, keeping the ankle joint flexible prevents contractures that could limit your movement permanently.
When Surgery Is Considered
Surgery is typically considered when symptoms persist beyond three months without meaningful improvement, or when imaging reveals a structural cause like a cyst or mass compressing the nerve. The most common procedure is surgical decompression, where the tissue compressing the nerve at the fibular head is released.
Outcomes for decompression are generally favorable. Published surgical series report improvement rates of 73% to 95% for motor weakness, 63% to 100% for pain, and 50% to 68% for abnormal sensations like tingling or burning. In one study, 92% of operated limbs showed improvement in motor strength. Pain responded well too, with 84% of patients reporting relief. Abnormal sensations were the most stubborn symptom, improving in about 65% of cases.
In severe injuries where the nerve has been cut or destroyed, nerve grafting or tendon transfer surgery may be options. Tendon transfers reroute a working tendon to take over the job of lifting the foot, bypassing the damaged nerve entirely.
Recovery Timeline
How quickly you recover depends on the type and severity of the nerve injury. Demyelinating injuries, where the nerve’s insulation is damaged but the fiber is intact, can recover in weeks to a few months as the insulation regenerates. Axonal injuries, where the nerve fiber itself needs to regrow, take much longer.
Nerve regrowth typically begins about a month after the injury and proceeds at roughly 1 millimeter per day. Since the injury site at the fibular head may be 30 to 40 centimeters from the muscles in the foot, full axonal recovery can take many months to over a year. Younger people and those without underlying conditions like diabetes tend to recover more completely. The longer the nerve has been damaged before treatment begins, the lower the chances of full recovery, which is why early identification matters.
During the regrowth period, consistent use of an AFO and ongoing physical therapy protect your mobility and prevent secondary problems like ankle stiffness or falls. Many people regain meaningful function, though some residual weakness or numbness may persist depending on the severity of the original injury.