Tarsal tunnel syndrome is a condition that occurs when the posterior tibial nerve is compressed. This large nerve runs down the back side of the leg, passes behind the medial malleolus (the ankle bone on the big-toe side of the foot), and down to the underside of the foot, where it supplies sensation to the skin and motor function to the intrinsic foot muscles. Before entering the foot, the nerve passes through an area called the tarsal tunnel. The roof of the tunnel is a thick ligament called the flexor retinaculum. The tarsal tunnel also contains three important tendons, as well as the principal artery (the posterior tibial artery) and its accompanying veins.
People with tarsal tunnel syndrome commonly complain of pain and numbness on the outside portion of the bottom of the foot. The pain is often described as burning, aching, radiating, “pins and needles,” throbbing, or tingling, like an electrical shock. Occasionally it affects the toes, making it difficult for doctors to distinguish it from a neuroma. When pressure is put on this nerve, one may feel a burning or numbness on the bottom of the foot.
Tarsal Tunnel Syndrome Symptoms
Tarsal tunnel syndrome is most common among active adults, but it can occur in children. Key symptoms to look for when diagnosing tarsal tunnel syndrome include:
- A burning sensation on the sole of the foot
- Shooting pain that worsens as the day progresses
- Tingling on the sole of the foot
- Numbness on the sole of the foot
- Electric shock sensation
- Foot pain when driving
- Hot and cold sensations in the feet
Some of these symptoms tend to appear suddenly, especially after overuse of the feet by prolonged standing, walking, running, or beginning a new exercise program. Most symptoms are felt either on the inside of the ankle or on the bottom of the foot. Some people experience these symptoms in just one area of the foot, while others may feel them throughout their toes, arch, heel, and calf. Needless to say it can be a difficult disease to diagnose.
What Causes Tarsal Tunnel Syndrome?
Tarsal tunnel syndrome is caused by the entrapment or compression of the posterior tibial nerve. It’s important to understand that the area of the heel and ankle is very complex. This is the area where all muscles, bones, ligaments, tendons, and nerves enter the foot. There is a lot happening in a very small area, and slight changes can have profound effects. The posterior tibial nerve is the largest nerve in the foot, and when swelling in the foot occurs for any reason, this large soft nerve, which shares a small space with three less pliable tendons, will be the first structure to be compressed.
Anything that decreases the volume of the tarsal tunnel can cause compression and inflammation of the nerve, leading to these symptoms. It can be caused by an enlarged adjacent muscle, varicose veins, arterial aneurysm, cysts, bone spurs, abnormal biomechanics, ganglions, and some metabolic diseases (e.g., arthritis, diabetes). Injury is another common cause of tarsal tunnel syndrome, as scar tissue may form and entrap the posterior tibial nerve.
Who is Susceptible to Tarsal Tunnel Syndrome?
People who are more prone to developing tarsal tunnel syndrome:
- Those with abnormal foot mechanics, e.g., flat feet
- Adults over the age of 30
- Those with arthritis
- Those with abnormal blood vessels
- Those who suffer from back pain
- Those who have suffered an ankle injury
If you suspect tarsal tunnel syndrome and are prone to the condition, you should visit your doctor. Your doctor can make a proper diagnosis by looking at your medical history and performing a careful physical examination. Occasionally an electrical test called a nerve conduction test or electromyogram (EMG) will be necessary. Less frequently, an MRI test may be conducted, particularly if a benign tumor or cyst is suspected.
Diagnosing Tarsal Tunnel Syndrome
Your doctor will examine your foot to determine whether you’ve lost normal sensation on the sole of the foot. Another important diagnostic sign is called the Tinel’s sign. The doctor performs this test by tapping on the nerve to see if a shooting sensation similar to an electrical shock radiates into the foot or up the leg. The doctor will also feel along the symptomatic area to check for masses. If your doctor suspects a mass, advanced imaging tests will be ordered.
Tarsal Tunnel Syndrome Treatment
Treatment depends on the cause of the problem. The goal is to relieve pressure on the nerve. Your doctor will also want to reduce your pain and the swelling of the nerve. Treatment may include:
- Orthotics such as shoe inserts to support the arch and limit excessive motion
- Better-fitting shoes
- Corticosteroid or anesthetic injections
- NSAIDs—Non-Steroidal Anti-Inflammatory Drugs such as ibuprofen
- Plenty of rest and time spent off the foot
- Restricting movement with a cast
- Vitamin B supplements
- Strengthening of the calf muscle, tibialis anterior, tibialis posterior, peroneus, and short toe flexors
- Surgical removal of the mass, if present
Surgical treatment for this condition may be necessary. During the procedure, an incision is made behind and below the inside of the ankle. The doctor then cuts the flexor retinaculum to give the nerve room for expansion. If a mass is present on the nerve, it will be removed at that time. After surgery, the ankle joint is immobilized and the patient typically needs to use crutches for a week or two. The foot is kept elevated to reduce swelling.
Nerves injured by entrapment regenerate slowly, which means the healing process may take up to a year. Unfortunately, if the tarsal tunnel syndrome is severe, there is a chance of permanent nerve damage. If this occurs, complete restoration of normal sensation and normal motor function may not be possible. This is especially true in patients with diabetes. Nerve medications such as gabapentin are sometimes helpful in these difficult cases.
Complications of Tarsal Tunnel Syndrome
As with any surgical procedure, excessive bleeding and infection are possible, but not very common. Diabetics may experience poor wound healing. The most common problem is incomplete pain relief, usually due either to a long-standing problem such as diabetes, or nerve compression in other areas, such as the lower back. Most people experience no complications. In fact, complications occur in only 13 percent of patients after surgery.
Talking to Your Doctor
Here are some questions you may want to ask your doctor about tarsal tunnel syndrome:
- If I need surgery, how long will it be before I can return to my normal activities?
- Will you be the surgeon? If so, how often do you perform this procedure?
- During non-surgical treatment, what signs should I watch for that may indicate the treatment is not working? How long should I wait to contact you if this happens?
- What can I do to prevent this syndrome from recurring?