What are the symptoms and treatment options for peroneal nerve entrapment, particularly in patients with a history of trauma, repetitive ankle or knee flexion, or underlying conditions like diabetes?

Peroneal Nerve Entrapment: Clinical Presentation and Management

Symptoms and Clinical Presentation

Peroneal nerve entrapment presents with distinct symptoms depending on which branch is affected—the common peroneal nerve (CPN), superficial peroneal nerve (SPN), or deep peroneal nerve (DPN)—with foot drop, lateral leg pain, and dorsal foot numbness being the cardinal features. 1

Superficial Peroneal Nerve Entrapment

• Numbness and tingling over the dorsum of the foot (sparing the first web space), which increases with activity such as walking, running, and squatting 2
• Lateral leg pain in the lower lateral one-third of the leg, typically 9-10 cm above the lateral malleolus 2, 3
• Positive Tinel's sign at the site of entrapment with radiating pain into the foot 2, 3
• Visible soft tissue bulge over the anterolateral aspect of the leg that increases with resisted ankle dorsiflexion or weight bearing 2
• Tenderness over the bulge or distally over the terminal sensory branches 2

Common Peroneal Nerve Entrapment

• Foot drop (present in approximately 60% of cases) 4
• Ankle instability (present in approximately 50% of cases) 4
• Pain and numbness of the lower extremity 1

Deep Peroneal Nerve Entrapment

• Compression typically occurs as the nerve crosses underneath the extensor retinaculum 1
• Presents with weakness of ankle and toe dorsiflexion 1

Diagnostic Approach

Clinical Examination Findings

• Decreased sensation to light touch and pinprick in the distribution of the affected nerve branch 2
• Gait abnormalities and decreased strength on motor testing 1
• Three positive provocation tests should be performed to confirm SPN entrapment 3

Electrodiagnostic Studies

• Motor nerve conduction studies and electromyography assist in diagnosis and prognosis 1
• Unrecordable evoked response or prolonged distal latency of the terminal sensory branches confirms SPN entrapment 2
• These studies are particularly important to exclude other etiologies such as entrapment syndromes at different locations 5, 6

Diagnostic Nerve Blocks

• Ultrasound-guided diagnostic nerve injection can confirm the diagnosis when clinical suspicion is high 7

Treatment Algorithm

First-Line Conservative Management

Conservative treatment should be attempted for 2-4 months before considering surgical intervention, as many cases resolve with activity modification and removal of external compression. 4, 1

• Remove any external compression sources (tight footwear, leg crossing, prolonged kneeling) 1
• Activity modification to avoid repetitive ankle or knee flexion 1
• Physical therapy including pain modalities, soft tissue mobilization, and neural mobilization can achieve complete pain resolution in selected cases 3
• Provide stability to unstable joints if ankle instability is present 1
• Anti-inflammatory measures to reduce local inflammation 1

Timing for Surgical Intervention

Surgical decompression should be considered after 2 months without recovery and after 4 months when recovery is slow. 4

• Surgical decompression by fasciotomy at the site of entrapment provides complete symptomatic relief in the majority of cases 2, 4
• Immediate relief of symptoms was achieved in approximately 58% of cases, with slower relief in 42% 4
• Microsurgical decompression is a newer option, though large outcome studies are lacking 1

Advanced Interventional Options

For refractory cases not responding to conservative management or surgery, pulsed radiofrequency (PRF) neuromodulation provides long-lasting pain relief without neural ablation. 7

• PRF is gaining popularity for entrapment neuropathies as it does not cause neural ablation unlike conventional radiofrequency ablation 7
• Percutaneous peripheral nerve stimulation is an emerging option, though outcome data are limited 1

Special Considerations in Diabetic Patients

Critical Diagnostic Caveat

Patients with diabetes and peripheral neuropathy require careful evaluation, as they may have painless foot drop or entrapment due to poor pain proprioception, and asymmetrical symptoms should always prompt investigation for focal entrapment rather than assuming symmetric diabetic neuropathy. 5, 6

• Diabetic peripheral neuropathy is invariably symmetrical; asymmetrical symptoms mandate evaluation for other etiologies including entrapment syndromes 5, 6, 8
• Up to 50% of diabetic peripheral neuropathy may be asymptomatic, increasing risk for unrecognized injuries 9
• Patients with diabetes and neuropathy may walk without discomfort despite fracture or nerve injury 5

Imaging in Diabetic Patients with Trauma

• Radiographs are the initial imaging study when fracture is suspected in patients with diabetic neuropathy or neurologic compromise, as these patients may have no pain or point tenderness 5
• Standard clinical decision rules (Ottawa rules) should not be applied in patients with neuropathy 5

Common Etiologies to Recognize

• Post-surgical (50% of cases, particularly after knee operations) 4
• Trauma including tibial fractures and ankle sprains 4
• Repetitive activities including excessive climbing or prolonged cross-legged sitting 4
• Idiopathic (approximately 17% of cases) 4