TARSAL TUNNEL SYNDROME
The tarsal equivalent of carpal tunnel syndrome
compression of the tibial nerve as it passes through the tarsal tunnel.
The tibial nerve is the major branch of the sciatic nerve
formed above the knee following division of the common peroneal nerve.
Its divisions are
      • the medial and lateral plantar nerves.
      • the medial calcaneal nerve and
      •the inferior calcaneal nerve

There is some variation in the location of these nerve divisions which may occur either prior, during or after passage through the tarsal tunnel.

A number of causes of tarsal tunnel have been described but the most common are:
      • Synovial cysts or ganglia
      • Lipoma
      • neurilemmoma
      • tenosynovitis
      • accessory muscles

Clinically there is tenderness along the medial aspect of the foot
which may be associated with sensory disturbances
particularly on the plantar aspect of the foot.

Synovial cysts arise in the region of the adjacent ankle joint, posterior subtalar joint or talonavicular joint.
Ganglion cysts may arise from any of the adjacent ligamentous structures.

An accessory soles muscle and new bone formation around a talocalcaneal coalition are other potential causes.

OTHER NERVES
Two other nerves that are important on the medial aspect of the ankle are the medial and inferior calcaneal nerves.
The inferior calcaneal nerve innervates:
      • plantar fascia
      • motor innervation to the flexor digitorum brevis
      •, the quadrates plantae and
      • the abductor digit minimi.

It passes along the medial border of the os calcis
between abductor hallucis and quadrates plantae muscle.
then in a soft tissue tunnel between abductor hallucis and flexor digitorum brevis
before reaching the plantar fascia.

The nerve may become entrapped particularly if there is muscle hypertrophy leading to symptoms which mimic plantar fasciopathy. The most common cause is compression as it traverses underneath the heel by a large plantar spur either in isolation or in association with plantar fasciitis.
In the absence of a specific compression cause, chronic traction is assumed to underlie symptoms.
A positive Tinel's sign over the nerve aids diagnosis.
Compression may lead to atrophy of Ab Dig Min (

The medial calcaneal nerve may be injured during surgical pin placement.
Neuroma of this nerve may also underlie heel pad symptoms.