Root Origin
- Spinal nerve roots: L4, L5, S1 (via the common peroneal nerve, from the sciatic nerve)
- Plexus: Sacral plexus (through the sciatic nerve → common peroneal nerve)
- Type: Mixed (motor and sensory)
Course
- Division from common peroneal. The superficial peroneal nerve branches from the common peroneal nerve as it wraps around the fibular neck, separating from the deep peroneal nerve within or just deep to the peroneus longus.
- Lateral compartment. The nerve descends through the lateral compartment of the leg between the peroneus longus and peroneus brevis, supplying both muscles. It lies between the peroneal muscles and the fibula.
- Fascial exit point. Approximately 10-12 cm above the lateral malleolus, the nerve pierces the deep fascia (crural fascia) to become subcutaneous on the anterolateral leg. This fascial exit point is the primary entrapment site. Once subcutaneous, the nerve is easily palpable in thin individuals — rolling it against the underlying fascia reproduces symptoms in entrapment cases.
- Anterolateral leg and dorsal foot. After becoming subcutaneous, the nerve divides into the intermediate dorsal cutaneous nerve and the medial dorsal cutaneous nerve, which supply the dorsum of the foot — all areas except the first web space (deep peroneal territory) and the lateral border (sural nerve territory).
Motor Distribution
| Muscle | Action | Notes |
|---|---|---|
| anatomy/muscles/peroneus-longus | Eversion, plantar flexion of the first ray | Tendon crosses under the foot to stabilize the first metatarsal head against the ground; critical for medial arch support |
| anatomy/muscles/peroneus-brevis | Eversion, weak plantar flexion | Attaches to the base of the 5th metatarsal; avulsion fractures at this site are common in ankle sprains |
Sensory Distribution
- Anterolateral leg. After piercing the deep fascia, the nerve supplies a strip of skin on the anterolateral leg between the fascial exit point and the ankle.
- Dorsum of the foot. The terminal branches (intermediate and medial dorsal cutaneous nerves) supply the dorsum of the foot, including the dorsal surfaces of toes 2-5 (proximal phalanges). The first web space is excluded (deep peroneal territory), and the lateral border of the foot is excluded (sural nerve territory).
- Clinical significance: The superficial peroneal nerve provides the broadest sensory territory on the dorsal foot. Numbness over the dorsum of the foot — especially after ankle sprains — is this nerve until proven otherwise. The dorsal foot is the area patients notice most because they see it when looking down.
Entrapment Sites
1. Fascial Exit Point (Anterolateral Leg)
- Location: Approximately 10-12 cm above the lateral malleolus, where the nerve pierces the deep crural fascia to become subcutaneous
- Structure: The fascial opening can compress the nerve. The nerve may angulate sharply as it transitions from the intramuscular compartment to the subcutaneous plane. Ankle sprains with associated fascial scarring, lateral compartment syndrome (chronic), and muscle herniation through the fascial defect can all compress the nerve at this point.
- Presentation: Anterolateral leg pain and dorsal foot numbness. Pain worsens with plantar flexion and inversion (which tenses the nerve at the fascial exit). Tinel's sign at the fascial exit reproduces dorsal foot paresthesia. In athletes, symptoms are exercise-dependent and build during running.
- MT relevance: After ankle sprains, scar tissue at the fascial exit can entrap the nerve. Patients with persistent dorsal foot numbness weeks after an ankle sprain may have post-traumatic superficial peroneal nerve entrapment — not just residual swelling. Fascial release around the exit point can improve symptoms. The nerve is palpable subcutaneously at this level — rolling it against the fascia reproduces symptoms in positive cases.
2. Ankle Inversion Sprain (Traction Injury)
- Location: Along the anterolateral leg and ankle, where the nerve is stretched during forced inversion
- Structure: Inversion sprains stretch the superficial peroneal nerve along with the lateral ankle ligaments. The nerve is tethered at the fascial exit point, creating a fixed point around which the nerve is stretched.
- Presentation: Dorsal foot numbness following an ankle sprain. The patient reports numbness that persists after the swelling has resolved. Often attributed to "swelling" when it is actually nerve stretch injury.
- MT relevance: Assess dorsal foot sensation in every ankle sprain patient. Persistent numbness beyond 4-6 weeks suggests nerve involvement. Nerve glides for the superficial peroneal nerve (eversion with dorsiflexion) can improve neural mobility and promote recovery.
Clinical Tests
| Test | Procedure | Positive Finding | What It Tells You |
|---|---|---|---|
| Resisted eversion | Patient everts the foot against resistance. | Weakness of eversion compared to the opposite side. | Peroneus longus and brevis function — superficial peroneal nerve. Isolated eversion weakness without dorsiflexion weakness suggests superficial peroneal involvement alone (not common peroneal). |
| Dorsal foot sensation | Light touch across the dorsum of the foot (excluding first web space and lateral border). | Decreased sensation across the dorsal foot. | Superficial peroneal sensory territory. Test multiple areas — the territory is broad and should be consistently altered if the nerve is involved. |
| Tinel's at fascial exit | Palpate the anterolateral leg approximately 10-12 cm above the lateral malleolus. Tap over the nerve as it exits the fascia. | Tingling radiating to the dorsal foot. | Nerve irritability at the fascial exit point — the most common entrapment site. The nerve is often palpable as a thin cord at this level in lean individuals. |
| Plantar flexion-inversion stretch | Passively plantar flex and invert the ankle. | Reproduction of anterolateral leg pain or dorsal foot tingling. | Tensions the superficial peroneal nerve by stretching it at the fascial exit and along its subcutaneous course. Analogous to neurodynamic testing for upper limb nerves. |
Clinical Notes
- Ankle sprains commonly injure this nerve. The superficial peroneal nerve is vulnerable during ankle inversion sprains because inversion stretches the nerve at its fascial tether point. Studies suggest that nerve injury occurs in 10-17% of ankle sprains. Persistent dorsal foot numbness after a sprain is often attributed to "bruising" or "swelling" when it is actually neurapraxia. Always test dorsal foot sensation as part of your ankle sprain assessment — it takes seconds and changes your understanding of the injury.
- Post-sprain rehabilitation should include nerve glides. Standard ankle sprain rehabilitation (RICE, bracing, proprioceptive training, peroneal strengthening) does not specifically address neural involvement. Adding superficial peroneal nerve glides — gentle eversion with dorsiflexion, sliding the nerve through the fascial exit — can improve outcomes when numbness is present.
- Muscle herniation at the fascial defect. In some individuals, the peroneal muscles herniate through the fascial opening where the nerve exits. The herniation is visible as a soft bulge on the anterolateral leg during muscle contraction. This can compress the nerve intermittently. Patients report symptoms that come and go with activity. Palpate the anterolateral leg during active dorsiflexion to check for muscle herniation.
- Distinguish superficial from common peroneal involvement. Superficial peroneal nerve entrapment alone: eversion weakness, dorsal foot numbness, NO dorsiflexion weakness. Common peroneal nerve palsy at the fibular head: eversion AND dorsiflexion weakness, dorsal foot AND first web space numbness. The presence or absence of dorsiflexion weakness is the key differentiator.
Related Nerves
- anatomy/nerves/deep-peroneal-nerve — The other terminal branch of the common peroneal nerve. Deep peroneal takes the anterior compartment (dorsiflexion); superficial peroneal takes the lateral compartment (eversion). Their sensory territories divide the dorsal foot.
- anatomy/nerves/common-peroneal-nerve — Parent trunk. A common peroneal lesion at the fibular head produces combined deep and superficial peroneal deficits.
- anatomy/nerves/sural-nerve — Supplies the lateral foot border and posterolateral leg — the territory adjacent to the superficial peroneal's dorsal foot territory. The boundary between the two runs along the lateral foot.
Key Takeaways
- Supplies the peroneals (eversion) and most of the dorsal foot sensation — eversion weakness without dorsiflexion weakness isolates this nerve from common peroneal involvement.
- Pierces the deep fascia 10-12 cm above the lateral malleolus — this fascial exit point is the primary entrapment site and is palpable in lean individuals.
- Ankle inversion sprains injure this nerve in 10-17% of cases — always test dorsal foot sensation in sprained ankles, and add nerve glides to rehabilitation when numbness is present.
- Persistent dorsal foot numbness weeks after an ankle sprain is neural, not just residual swelling.