Tibial nerve
Nervus tibialis
Also known as: medial plantar nerve, lateral plantar nerve, sural nerve, medial popliteal nerve
The larger terminal branch of the sciatic nerve (L4–S3). It descends through the popliteal fossa and the posterior compartment of the leg, passes behind the medial malleolus in the tarsal tunnel, and supplies the plantarflexors, the toe flexors and, through the plantar nerves, the sole of the foot.
Overview
The tibial nerve continues the sciatic nerve vertically through the popliteal fossa. It is the most superficial of the central structures there, with the popliteal vein deep to it and the popliteal artery deepest. In the fossa it supplies gastrocnemius, soleus, plantaris and popliteus. It gives the medial sural cutaneous nerve, which joins a branch of the common fibular nerve to form the sural nerve. The sural nerve supplies the lateral ankle and lateral foot, and is used for nerve biopsy and grafting.
The tibial nerve passes under the tendinous arch of soleus into the posterior compartment, where it runs with the posterior tibial vessels between the superficial and deep muscle layers. It supplies tibialis posterior, flexor digitorum longus and flexor hallucis longus. It passes behind the medial malleolus, under the flexor retinaculum, through the tarsal tunnel. There it gives medial calcaneal branches to the heel and divides into two plantar nerves:
• the medial plantar nerve, which is like the median nerve of the hand: it supplies abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, the first lumbrical and the skin of the medial 3½ toes;
• the lateral plantar nerve, which is like the ulnar nerve: it supplies the remaining intrinsic foot muscles and the skin of the lateral 1½ toes.
- Location
Popliteal fossa → posterior compartment of the leg → tarsal tunnel (posterior to the medial malleolus) → sole of the foot.
Anatomy
- Innervation
- Motor: all the muscles of the posterior compartment of the leg and all the intrinsic muscles of the sole.
• Sensory: the heel and sole (plantar nerves) and, via the sural nerve, the lateral ankle and foot.- Nerve roots
L4, L5, S1, S2, S3 (anterior divisions).
- Course
Apex of the popliteal fossa → through the fossa superficial to the popliteal vessels → deep to the soleal arch → posterior compartment with the posterior tibial vessels (on tibialis posterior) → behind the medial malleolus under the flexor retinaculum (tarsal tunnel) → medial and lateral plantar nerves.
- Branches
- Muscular: gastrocnemius, soleus, plantaris, popliteus, tibialis posterior, flexor digitorum longus and flexor hallucis longus.
• Cutaneous: the medial sural cutaneous nerve (to the sural nerve) and medial calcaneal branches.
• Articular branches to the knee and ankle.
• Terminal branches: the medial and lateral plantar nerves.
Function
- Plantarflexion of the ankle (gastrocnemius, soleus), for push-off in walking and standing on tiptoe
- Inversion of the foot (tibialis posterior)
- Flexion of the toes; intrinsic foot muscle support of the arches
- Sensation of the sole and heel
- Afferent and efferent limbs of the ankle (Achilles) reflex (S1–S2)
Clinical significance
Tibial nerve lesion
Injury in the popliteal fossa (knee dislocation, penetrating trauma, Baker cyst) causes:
• loss of plantarflexion (the patient cannot stand on tiptoe);
• weak inversion and toe flexion;
• a calcaneovalgus foot (dorsiflexed and everted by the unopposed anterior and lateral compartments);
• a shuffling gait with no push-off;
• an absent ankle reflex;
• sensory loss of the sole.
Tarsal tunnel syndrome
Compression of the tibial nerve or its plantar branches under the flexor retinaculum behind the medial malleolus causes burning pain and paraesthesia of the sole, worse at night or on standing. Tinel sign is positive behind the medial malleolus. Causes include ganglia, varicosities, trauma, flat foot and tenosynovitis.
Mnemonics
Tarsal tunnel contents
"Tom, Dick And Very Nervous Harry": Tibialis posterior, flexor Digitorum longus, posterior tibial Artery, Vein, tibial Nerve, flexor Hallucis longus (from anterior to posterior behind the medial malleolus).
Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.