The tibial nerve is one of two main muscular branches of the sciatic nerve that innervates the triceps surae, plantaris, popliteus, tibialis posterior, flexor digitorum longus and flexor hallucis longus muscles.
At the level of the foot, the tibial nerve divides into two branches. The first one is the medial plantar nerve, which innervates the following muscles:
The second branch is the lateral plantar nerve, which innervates the muscles below:
The tibial nerve continues on and passes through the center of the popliteal fossa and runs below the tedinous arch of the soleus muscle to the superficial and deep plantar flexors. More specifically, in the deep posterior compartment, the tibial nerve continues distally in a neurovascular bundle and passes through the tarsal tunnel, accompanied by deep flexor tendons.
There is a useful mnemonic to remember the order structures that pass through the tarsal tunnel (from anterior to posterior);
Tom, Doug And Very Nervous Harry
- Tibialis posterior flexor
- Digitorum longus
- Artery (posterior tibial)
- Vein (posterior tibial)
- Nerve (tibial)
- flexor Hallucis longus
As it travels through the posterior leg, the tibial nerve gives off a cutaneous branch called the medial sural cutaneous nerve (which is continuous with the sural nerve).
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Once it has passed through the tunnel, the tibial nerve then divides into the lateral and medial plantar nerves, which supply all of the muscles on the plantar side of the foot. Before it divides, the tibial nerve gives off several cutaneous branches such as:
- lateral calcaneal branches
- medial calcaneal branches
- lateral dorsal cutaneous nerve
The medial plantar nerve supplies the abductor hallucis, the flexor digitorum brevis, the flexor hallucis brevis, and the first lumbrical. Cutaneous distribution of the medial plantar nerve is to the medial sole and medial three and one half toes, including the nail beds on the dorsum (similar to the cutaneous distribution of the median nerve in the hand). A good mnemonic is “LAFF muscles” (First Lumbrical, Abductor Hallucis, Flexor digitorum brevis, Flexor hallucis brevis).
The lateral plantar nerve supplies the quadratus plantae, the flexor digiti minimi, the adductor hallucis, the interossei, three lumbricals, and abductor digiti minimi. Cutaneous innervation is to the lateral sole and lateral one and one half toes (similar to the cutaneous distribution of the ulnar nerve in the hand).
Tarsal tunnel syndrome
Compression of the tibial nerve or its terminal branches will lead to an entrapment syndrome known as tarsal tunnel syndrome. This syndrome results in pain and sensory disturbances that affects the sole of the foot, and can cause palsies of the intrinsic foot muscles. This can also result from severe nerve trauma connected to fractures of the tibial shaft or medial malleolus.