Tibial Nerve: The tibial nerve is a branch of the sciatic nerve.
Nerve roots: L4-S3
Motor: Innervates the posterior compartment of the leg muscle.
Sensory: Innervates the skin of the posterolateral side of the leg, a lateral side of the foot, and the sole of the foot.
Anatomical Course of the Tibial Nerve
The tibial nerve is a part of the sciatic nerve and begins at the apex of the popliteal fossa. It travels within the popliteal fossa, giving off branches in the superficial posterior compartment of the leg muscles. Here, the tibial nerve further gives rise to branches that contribute towards the sural nerve, that innervates the posterolateral aspect of the leg muscle.
The tibial nerve remains its course down the leg, posterior to the tibia. While its descent, it provides the deep muscles of the posterior leg.
At the foot, the nerve crosses posteriorly and inferiorly to the medial malleolus, within a structure known as the tarsal tunnel. This tunnel is capped superiorly by the flexor retinaculum. Inside this tunnel, branches arise from the tibial nerve to provide cutaneous innervation to the heel.
Now distal to the tarsal tunnel, the tibial nerve terminates by branching into sensory, that innervates the sole of the foot.
Function of the Tibial Nerve
The tibial nerve innervates all in the posterior compartment of the leg muscles. They are divided into a deep and superficial compartment:
- Popliteus Muscle – Laterally rotates the femur on the tibia to unlock the knee joint.
- Flexor Hallucis Longus Muscle – Flexes the big toe and plantar flexes the ankle joint.
- Flexor digitorum Longus Muscle – Flexes the other digits and plantar flexes the ankle joint.
- Tibialis Posterior Muscle – Inverts the foot and plantar flexes the ankle joint.
- Plantaris Muscle – Plantar flexes the ankle joint.
- Soleus Muscle – Plantar flexes the ankle joint.
- Gastrocnemius Muscle – Plantar flexes the ankle and flexes the knee joint.
In specific popliteal fossa, the tibial nerve provides the cutaneous branches. These merge with branches from the common fibular nerve to form the sural nerve. This sensory nerve supplies the skin of the posterolateral side of the leg furthermore the lateral side of the foot.
The tibial nerve further supplies all the sole of the foot via three branches:
- Medial Plantar Nerve: Supplies the plantar surface of the medial three and a half digits, and the associated sole area.
- Medial calcaneal branches: These arise inside the tarsal tunnel and innervate the skin over the heel.
- Lateral Plantar Nerve: Supplies the plantar surface of the lateral one and a half digits, and the associated sole area.