The Anatomy of the Tibial Nerve

• Updated on: 2020-12-10
• Read original article here

The tibial nerve is a branch of the sciatic nerve that runs down the back of your leg and into the foot. It's involved in a condition called tarsal tunnel syndrome that's sometimes found in people with osteoarthritis, rheumatoid arthritis, or ankle deformities due to injury. Anatomy

The sciatic nerve, which is involved in the painful condition called sciatica, is the largest nerve in the human body. It emerges from the spinal column in your lower back, then extends down through the buttock and into the leg.

At the back of your knee, it divides into two branches:

The tibial nerve
The common peroneal (or fibular) nerve

A nerve isn't just a single line—it branches off to connect to skin, muscles, and connective tissues.

As the tibial nerve continues down from the knee, it sends branches to the muscles along the back of the calf as well as deep muscles in the leg.

It then runs along the Achilles tendon and enters the foot through a structure called the tarsal tunnel, where it further branches to the skin of your heel. It then exits the tunnel and divides into more sensory branches that go to the sole of the foot.
Function

The tibial nerve is both a motor nerve, meaning it sends signals that make muscles move, and a sensory nerve, which means it's involved in detecting sensation on the skin.
Motor Function

The tibial nerve sends signals from the brain to the muscles in the back of your leg to get them to move. It controls movement in the following muscles:

Popliteus
Flexor hallucis longus
Flexor digitorum longus
Tibialis posterior
Plantaris
Soleus
Gastrocnemius

These muscles rotate your leg inward and flex your knees, ankles, and toes. They provide a lot of the movements you need to walk.
Anatomy of the Lower Leg
Sensory Function

The parts of the nerve that serve the skin are called cutaneous branches. The tibial nerve has cutaneous branches that supply sensation to the skin in an arc from the outside of your knee, down the back of the calf, to the outside portion of the foot and most of the sole of the foot.

Just in front of the heel, the tibial nerve divides into the medial plantar nerve, which sends signals to the big toe and the two closest to it, and the lateral plantar nerve, which sends impulses to the two outer toes.
Associated Conditions

The primary condition associated with the tibial nerve is tarsal tunnel syndrome, which is similar to carpal tunnel syndrome (in the hands), but far less frequent. It's also known as posterior tibial neuralgia.

The tarsal tunnel is a narrow opening in the foot that the nerve runs through. The tunnel is covered by a fibrous band called the flexor retinaculum.

If the tarsal tunnel becomes narrowed, such as by inflammation, it can compress the nerve. Causes of tunnel narrowing can include anything that puts pressure on the nerve, such as:

Injury to the ankle or tendons
Osteoarthritis or rheumatoid arthritis
Other systemic diseases including hypothyroidism (low thyroid function), diabetes, or any inflammatory illness that impacts the foot or ankle
Bone spurs
Ganglion cysts
Varicose veins
Flat feet or an especially high arch

However, doctors aren't always able to find a cause of tarsal tunnel syndrome.

Compression causes pain and loss of function. The primary symptoms of tarsal tunnel syndrome is a type of nerve pain and abnormal nerve sensations called paresthesia.

In this condition, paresthesia is often characterized by a burning or tingling in the ankle and sole of the foot, often reaching the toes and sometimes radiating a little way up the leg. It worsens with walking, and possibly standing, but usually gets better with rest. However, as the disease progresses, pain can occur at nighttime, interfering with sleep. Sometimes you may feel an electric, "zingy" tingle with tapping the site of compression.

Tarsal tunnel syndrome can be substantially debilitating and make it difficult to walk. In severe cases, or if it goes untreated for a long time, the nerve can become permanently damaged.

Nerve damage anywhere along the tibial nerve can cause varying degrees of pain, loss of sensation, and weakness in the muscles served by the nerve.

Tarsal tunnel syndrome and neuropathy can be diagnosed via symptoms, a physical exam, tests, and scans.

After learning what symptoms you're experiencing, your doctor will examine you to see if you have:

Weakness in the ankle, foot, or toes
An inability to twist your ankle inward, push down on your foot, or curl your toes
Pain or paresthesia with certain movements

They may order tests and imaging, such as:

Electromyography (EMG): Typically done just after the nerve conduction test, EMG records the electrical activity in your muscles when the nerves are activated. It can show how your muscles and nerves are functioning together and also can differentiate between a muscle-based problem and a nerve-based problem.
Magnetic resonance imaging (MRI): MRI can identify growths that may be compressing the nerve by creating a detailed image using magnets and radio waves.
Computerized tomography (CT) scan: To identify bone growths and problems with your veins.
Nerve conduction tests: To measure how quickly electrical impulses are flowing through your nerves. Slow signals can be an indication of nerve damage. However, this diagnostic method is controversial. According to a 2012 review of studies on the condition, results of this test often appear normal even in people who do have tarsal tunnel syndrome, leading to misdiagnosis and delays in treatment.1

Depending on your symptoms, your doctor may also order X-rays and/or blood tests.
Treatment

In many cases, people get relief from the pain of tarsal tunnel syndrome by taking anti-inflammatory drugs and wearing shoes that fit well and provide good support. Your doctor may suggest orthopedic sandals or custom insoles (especially if you have flat feet or another foot problem.)

Also, icing the ankle, resting the foot, and avoiding activities that cause pain can give the foot time to heal.

If that doesn't work, other treatment options may include:

Physical therapy to stretch and strengthen the foot and promote blood flow, which can speed up healing.
Injection with a local anesthetic (to kill pain) or a corticosteroid medication (to relieve inflammation)
Surgery to cut the flexor retinaculum and release pressure on the nerve, or to move the nerve itself

Treatment of tarsal tunnel is important. If it's left untreated, possible complications can include

Foot deformity
Loss of movement in the toes, which can be partial or complete
Loss of sensation in the foot or toes, which can be partial or complete

As a complication of sensation loss, unnoticed injury to the affected part, which can lead to further damage or infection.

Early diagnosis and treatment, on the other hand, increases the likelihood that you'll be able to control the symptoms well and prevent substantial pain and disability. Be sure to let your doctor know if you're having symptoms that could suggest tarsal tunnel syndrome.