Common Peroneal Nerve Decompression
Common peroneal nerve decompression is a surgical procedure that releases the common peroneal nerve from compression at the fibular head — the bony prominence just below and to the outer side of the knee — relieving foot drop, outer leg numbness, and peroneal nerve pain.
Overview
What is Common Peroneal Nerve Decompression?
Common peroneal nerve decompression is a surgical procedure that releases the common peroneal nerve from compression at the fibular head — the bony prominence just below and to the outer side of the knee — relieving foot drop, outer leg numbness, and peroneal nerve pain.
The common peroneal nerve wraps around the fibular head with very little soft tissue protection, making it the most vulnerable peripheral nerve in the lower limb to compression. When compressed — from habitual leg crossing, prolonged squatting, tight bracing, or a ganglion cyst — it causes the characteristic clinical syndrome of foot drop (inability to lift the front of the foot), lateral leg numbness, and outer knee pain.
Surgical decompression releases the fibrous tunnel and any compressing structures at the fibular head, allowing the nerve to recover and foot drop to resolve over the following months.
When is Surgery Recommended?
- Foot drop not recovering after 6 to 8 weeks of conservative management with removal of compression
- Structural cause identified on imaging — ganglion cyst, fibrous band, or intrinsic tunnel stenosis
- Severe or complete foot drop significantly impairing mobility and safety
- Progressive neurological deficit
Procedure
Preoperative Preparation
Nerve conduction studies and EMG confirm peroneal nerve injury at the fibular head, assess severity, and exclude L4/L5 radiculopathy (disc herniation or spinal stenosis causing foot drop). MRI of the knee and fibular head identifies structural causes. MRI lumbar spine rules out a spinal cause. Blood thinners are ceased. The procedure is a day case.
What Happens During Peroneal Nerve Decompression?
The procedure is performed under general anaesthesia with the patient supine and the knee slightly flexed. A small longitudinal incision (approximately 5 to 8 cm) is made along the outer aspect of the knee overlying the fibular head. The peroneal nerve is carefully identified proximal to the fibular head and traced through the fibrous tunnel formed by the origin of the peroneus longus muscle as it wraps around the fibular head.
The fibrous tunnel is divided, decompressing the nerve. Any additional fibrous bands, ganglionic tissue, or compressing structures are also released or excised. The nerve is inspected for any intrinsic pathology. For ganglion cysts, the cyst is fully excised to prevent recurrence. The wound is closed in layers. The duration of the operation is usually 45 to 60 minutes.
Outcomes & risks
Outcomes of Peroneal Nerve Decompression
Outcomes depend on the severity of nerve injury before surgery. For early, mild-to-moderate compression, sensory improvement is typically rapid and motor recovery excellent — foot drop resolves completely in the majority of patients. For severe or longstanding compression with significant axonal loss (demonstrated on EMG as denervation), motor recovery may be incomplete, and the AFO may be needed long-term. The earlier surgery is performed, the better the prognosis.
Risks and Complications
- Incomplete nerve recovery — depends on preoperative nerve injury severity, more common with longstanding or severe compression
- Wound infection — approximately 1%
- Haematoma — uncommon
- Sural nerve injury — the sural nerve runs nearby; injury causes numbness at the outer ankle and foot; rare with careful technique
- Recurrence — rare after complete release; more common if the underlying cause (ganglion) was not fully excised
Frequently Asked Questions — Peroneal Nerve Surgery Melbourne
Will my foot drop recover after surgery?
Recovery depends on the severity and duration of nerve injury before surgery. For mild-to-moderate, acute or subacute compression — complete or near-complete recovery of dorsiflexion strength is expected over 3 to 12 months. For severe or longstanding compression with significant axonal loss on EMG — motor recovery may be partial. Even partial recovery may dramatically improve function and reduce AFO dependence. Early surgical referral maximises recovery potential.
How do I know if my foot drop is from the knee or from my back?
Both lumbar disc herniation (L4/L5 nerve root compression) and peroneal nerve entrapment cause foot drop — but treatment is completely different. Peroneal nerve entrapment causes symptoms localised to the outer knee, leg, and foot, without back or buttock pain. Lumbar radiculopathy causes foot drop with associated back, leg, and calf pain (sciatica). Nerve conduction studies and EMG definitively localise the problem and distinguish between the two — this is an essential investigation before any surgical decision. MRI lumbar spine also rules out spinal nerve root compression.
How long will I need to wear the ankle foot orthosis?
The AFO is continued until adequate active dorsiflexion returns — typically demonstrated by the ability to clear the foot during normal walking without the AFO. This may take 3 to 12 months following surgery. Regular physiotherapy assessment guides the timing of AFO weaning.
Why Choose One Brain and Spine?
One Brain and Spine is a specialist neurosurgical group practice in Melbourne with expertise in peripheral nerve surgery. Our fellowship-trained neurosurgeons offer both endoscopic and open nerve decompression techniques, with a patient-centred approach and clear explanation of all options.
- Specialist neurosurgeons
- Endoscopic and open techniques — appropriate technique for each patient and nerve
- Patient-centred approach — clear diagnosis and treatment options
- All major health funds accepted