Peroneal Nerve Entrapment
Peroneal nerve entrapment, also called common fibular nerve entrapment, is a condition in which one of the major nerves of the leg becomes compressed or irritated. This nerve runs along the outside of the knee and down into the lower leg, where it controls movement and sensation in the front and side of the leg and the top of the foot.
Because the peroneal nerve plays a key role in lifting the foot and toes, entrapment can cause weakness, numbness, and even a condition known as “foot drop,” where patients have difficulty lifting the front of the foot while walking.
Understanding the Peroneal Nerve
The peroneal nerve is a branch of the larger sciatic nerve. It travels from the thigh, winds around the outside of the knee near the fibular head (a bony prominence just below the knee), and then splits into two smaller branches: the deep peroneal nerve and the superficial peroneal nerve. These branches provide sensation to parts of the lower leg and foot and control muscles that lift and stabilize the foot during walking.
Because the nerve passes through a tight space around the fibular head, it is especially vulnerable to compression.
Causes and Risk Factors
Several situations can lead to peroneal nerve entrapment:
- Prolonged leg crossing or squatting, which puts direct pressure on the outside of the knee.
- Injury or trauma such as a fracture of the fibula or knee dislocation.
- Rapid weight loss, which decreases protective fat around the nerve.
- Use of tight plaster casts or braces around the knee or leg.
- Space-occupying lesions like cysts or tumors near the fibular head.
- Repetitive motion or certain postures common in athletes or manual laborers.
Symptoms
The hallmark sign of peroneal nerve entrapment is foot drop—the inability to lift the front of the foot, leading to a high-stepping gait to avoid tripping. Other symptoms include:
- Numbness or tingling on the top of the foot and outer part of the lower leg.
- Weakness in the ankle and toes, especially when trying to pull the foot upward (dorsiflexion).
- Pain or discomfort along the outer knee or shin.
- Difficulty walking, running, or maintaining balance.
Diagnosis
Diagnosis begins with a medical history and physical exam, focusing on strength, reflexes, and sensation. Doctors may check for tenderness near the fibular head and test foot and ankle movement.
Additional tools include:
- Nerve conduction studies and electromyography (EMG): To assess nerve function and locate the site of entrapment.
- Imaging (MRI or ultrasound): To rule out tumors, cysts, or structural causes of compression.
Treatment Options
The approach to treatment depends on the cause and severity of nerve compression.
Conservative management may include:
- Avoiding prolonged leg crossing or pressure on the knee.
- Physical therapy to strengthen leg muscles and improve gait.
- Bracing or an ankle-foot orthosis (AFO) to support the foot in cases of foot drop.
- Anti-inflammatory medications or lifestyle adjustments to reduce nerve irritation.
Surgical treatment is considered when symptoms are severe, progressive, or do not improve with conservative care. Procedures may include:
- Nerve decompression: Releasing tight structures that compress the nerve.
- Removal of masses or cysts pressing on the nerve.
- Nerve repair or grafting in cases of traumatic injury.
Prognosis and Prevention
The outcome varies depending on the cause and how quickly treatment begins. Many patients recover well with early intervention, especially when compression is due to posture or external pressure. In cases of traumatic injury, recovery may take longer and sometimes requires surgery.
Preventive strategies include avoiding prolonged leg crossing, using protective padding during sports, and monitoring casts or braces for excessive tightness.
Peroneal nerve entrapment can have a major impact on mobility, but with early recognition and proper management, many patients regain strength, sensation, and confidence in walking. Recognizing the early signs—numbness, tingling, or weakness in the foot—can make a crucial difference in preventing long-term complications like persistent foot drop.
