Introduction 

What is tarsal tunnel syndrome?

Tarsal Tunnel Syndrome (TTS) is a neuropathy where the tibial nerve situated within the tarsal tunnel, has been impaired or compressed. Neuropathy occurs when the nerve endings are damaged and cause numbness among other symptoms. The tarsal tunnel is a passage in the ankle made up of bones and ligaments containing the nerves and blood vessels. 

TTS is a rare condition and is often underdiagnosed because it is mistaken for other neuropathies or foot diseases with similar symptoms. In this article, we will be exploring different diseases and conditions that can be confused for TTS and how we can tell them apart using physical exam, personal history, and diagnostic tools.

What is in a tarsal tunnel?

Figure 1. Illustration of a tarsal tunnel in the ankle. (Photo credit: Mortonsneuroma)

The tarsal tunnel consists of the following structures:

• Flexor Retinaculum – This is the tissue that holds two bones together within the joints
• Posterior tibial nerve – The nerve that runs through the tarsal tunnel and sends sensations through the ankle and feet 
• Posterior tibial artery – transports blood to the parts of the feet
• Posterior tibial veins – The branches of the posterior tibial artery that provide blood to the tissues of the feet 

All of these structures contribute towards functions of the foot, such as walking, running, and range of motion of the foot.

What happens in TTS? 

Compression of the tibial nerve

TTS is caused by tibial nerve compression, which branches out into the heel of the foot. When compressed, the tibial nerve can send a tingling or painful sensation down the heel and other regions of the foot where the tibial nerve branches off¹.

Causes of Tarsal Tunnel compression

• Trauma; around 43% of the cases have a history of ankle sprain that damages or injures the posterior tibial nerve or causes swelling that compresses the nerve²
• Lesions that compress the tibial nerve or the tarsal tunnel such as ganglion cysts, and varicose veins³
• Conditions, such as diabetes and hypothyroidism, can cause swelling within the arteries and veins in the tarsal tunnel and compress the tibial nerve

Clinical presentation of Tarsal Tunnel syndrome

Common symptoms

• Pain and burning sensation in the foot and ankle⁴
• Tingling in the tibial nerve distribution
• Worsening symptoms with prolonged standing or activity in addition to foot muscle weakness

Physical examination findings

• Tinel’s sign over the tarsal tunnel – A Tinel’s test is done by lightly tapping over the tarsal tunnel and any signs of pain will indicate that you have TTS
• Dorsiflexion-Eversion Test – A range of motion assessment is performed on the ankle to determine tibial nerve compression, which indicates TTS if you feel any pain or tingling. This assessment involves stretching the foot upwards and downwards 
• Look for signs of muscle weakness – Muscle weakness is seen in severe cases that are left untreated. When the tibial nerve is compressed, its nerve endings cannot send signals to the muscles of the feet resulting in muscle weakness

Conditions that are often confused for tarsal tunnel syndrome 

Conditions relating to the nerves

• Peripheral neuropathy – Peripheral neuropathy occurs when the nerves that lead to the hands and feet are damaged.⁵ Peripheral neuropathy can affect both feet like in TTS but does not present with a positive Tinel’s sign
• Complex regional pain syndrome (CRPS) – caused by trauma or surgery that damages the nerve. You might feel a burning and tingling sensation like in TTS, however, CRPS can present with skin colour changes and increased sweating, which is not seen in TTS⁶
• Morton’s neuroma – caused by compression of the nerve that runs between the bones within the tops of the feet, therefore, the pain is mainly in the forefoot⁷

Disorders relating to the muscles and bones 

• Posterior tibial tendon dysfunction (PTTD) – also known as flat foot deformity, is a progressive disorder, which can worsen over time. People with PTTD present with inner ankle pain⁸

Figure 2. Plantar fascia situated at the base of the foot and plantar fasciitis presenting at the heel (Photo credit: Sportshealth)

• Plantar Fasciitis – is the inflammation of the plantar fascia (situated at the base of the foot). This is often caused by continuous stress on the plantar fascia due to weight gain or excessive use of your feet.⁹ Unlike TTS, it is most painful in the morning with no burning or tingling sensation
• Achilles Tendinopathy – The Achilles tendon is a band of tissues that connects the bones in the foot to the muscle at the heel. It can be damaged by overexertion of the feet. Symptoms include pain at the back of the ankle and tenderness at the heel¹⁰ 
• Medial Calcaneal Nerve Entrapment – The medial nerve is a branch of the tibial nerve and can trigger symptoms similar to TTS. It is caused by nerve compression from trauma or excessive use. Its symptoms include heel pain that is distinct from the tibial nerve pathway¹¹

How do you know you have TTS? 

Patient history and physical examination

People with TTS usually complain about pain over the tarsal tunnel region in the ankle, the arches, and the heel of the feet. Other symptoms could be numbness, tingling or burning sensation, muscle weakness, and limping while walking. This would indicate to your healthcare provider to test for TTS. A Tinel’s test and dorsiflexion-eversion test would further point towards TTS and further tests would be done, which are discussed below.

Electrodiagnostic studies

Nerve conduction studies (NCS) 

NCS is performed by sending small electric pulses to the nerves and the nerve response is measured using a pad. People with TTS tend to show uncommon results that help understand the disease process and confirm the TTS diagnosis.

Electromyography (EMG)

EMG is used to study the electrical signal that occurs naturally within the muscles by placing a small needle within the muscle. This test can be used to confirm diagnosis when you are suspected of TTS, however, studies have found that cases with negative EMG improve after being treated for TTS.¹²

People with pacemakers or internal defibrillators, who use blood thinners, and are on medications for myasthenia gravis are encouraged to let their healthcare provider know before taking these tests to prevent any complications.

Diagnosing TTS using imaging

Magnetic resonance imaging (MRI) 

Figure 3. MRI imaging of ankle with a ganglion cyst (indicated with an arrow) (Photo credit: Radsource)

An MRI is a type of scan used to view detailed images of the body using magnetic waves. It is used to visualise the tarsal tunnel and its contents.¹³ As shown in figure 3, a ganglion cyst can be clearly seen as a white blob around the tarsal tunnel region of the ankle. This indicates that there is a cyst compressing the tibial nerve.

High-resolution ultrasound 

High-resolution ultrasound is another imaging tool used to see detailed images of the body using sound waves. This is a simpler and cheaper method than MRI, and it can provide quicker results than MRI.¹⁴ Hence, studies reveal that ultrasound is a viable option to determine the cause of TTS, such as finding cysts, muscle disorders that lead to TTS, or swelling of the tibial veins.

How to differentiate between TTS and its mimics?

Symptoms and physical presentation

TTS symptoms are localised to the ankle, arches, and heel of the feet while conditions such as plantar fasciitis present at the bottom of the heel and people with Morton’s neuroma have pain at the upper region of the soles. Essentially, the area where the pain is originating from helps decide whether you have TTS or another condition. 

Patterns seen in TTS and its mimics

TTS worsens after activities such as prolonged walking, standing or running as well as at night. On the other hand, peripheral neuropathy symptoms are constant and do not go away even while at rest. People with Achilles tendinopathy often complain about foot stiffness in the morning or after inactivity and do not complain of pain until after performing activities. A positive response to Tinel’s sign and pain during the dorsiflexion-eversion test will further help direct you towards a TTS diagnosis. 

Findings on imaging and electrodiagnostics

MRI scans can detect cysts (as seen in Figure 3) that compress on the tibial nerve causing TTS. Positive results in electrodiagnostic studies can confirm that the tibial nerve does not function normally. If negative results are seen in the studies, then it might be pointing towards more muscle-related or diseases related to blood vessels.

Treatment and management

• Disease management– It is recommended to apply ice to reduce inflammation and pain. Physical therapy and kinesiology tape are used to improve foot function and stability respectively. Orthopaedic shoes are recommended to take pressure off the tarsal tunnel
• Medication – Painkillers, such as NSAIDs, are recommended or topical lidocaine is used for pain relief. Steroid injections might be administered in extremely painful cases. Medications to treat neuropathy will also be prescribed 
• Surgery – This is a last resort and is usually performed on ganglion cyst to drain them and relieve the pressure off of the tibial nerve. Another method is to cut the tarsal tunnel to relieve the pressure on the tibial nerve

FAQ’s

What happens if TTS is left untreated?

Untreated TTS can result in permanent limp while walking, muscle loss or deformity and loss of function, for example, being unable to move your toes.

How do you differentiate between foot pain and nerve pain?

Nerve pain often feels like a burning or tingling sensation.

Summary 

TTS is a neuropathy caused by the compressions of the tibial nerve that can result in pain and tingling in the feet. It is often mistaken for other nerve-related or muscle-related disorders and diseases because the symptoms are similar. However, there are ways to differentiate between TTS and its mimics by looking at the pattern of the symptoms and performing electrodiagnostic tests and imaging to confirm TTS. Future research could focus on improving the diagnostic tools that can confirm TTS without misdiagnosing it for other neuropathies or tendonitis.