Tarsal tunnel syndrome occurs when the posterior tibial nerve becomes compressed as it passes through a narrow space on the inside of the ankle called the tarsal tunnel. This tunnel is bordered by bone on one side and a thick ligament (the laciniate ligament) on the other, leaving little room for swelling or structural abnormalities.
When the nerve becomes entrapped, swelling and scar tissue reduce its blood supply and impair its ability to glide with ankle motion. This leads to burning, tingling, numbness, or shooting pain on the bottom of the foot. Symptoms may worsen with standing or walking and may vary depending on which branch of the nerve is affected.
Common causes include trauma, excessive pronation that increases tension on the inside of the ankle, tendonitis of structures passing through the tunnel, or space‑occupying masses such as ganglion cysts or lipomas. Diagnosis is based on symptom distribution, tenderness behind the medial malleolus, a positive Tinel’s sign, nerve conduction studies, and imaging when a mass is suspected.
Treatment focuses on reducing pressure on the nerve. Orthotics help when over‑pronation is the underlying cause, while bracing or casting may be used after trauma to limit ankle motion. Anti‑inflammatory medication, corticosteroid injections, and nerve stimulation may provide relief. If conservative care fails, surgical release of the laciniate ligament and removal of any compressive tissue may be necessary to prevent permanent nerve damage.
Tarsal Tunnel Syndrome is the compression of the main nerve (posterior tibial nerve) that passes under the medial or inside part of the ankle. Peripheral nerves such as the nerves in the feet are richly endowed with their own blood supply and have the ability to stretch or shorten along with the movement of the accompanying joint; in this case the ankle joint.
When the nerve is entrapped in its tunnel the swelling that occurs around the nerve and the ensuing scarring of the nerve inhibit blood flow to the nerve. As the ankle joint continues to move the nerve is further compressed and the ability of the nerve to properly function is diminished.
The tarsal tunnel location is on the inside portion of the ankle, just below the medial malleolus, (the bone on the inside of the ankle.)
Below is an anatomical diagram of the band, known as the laciniate ligament represented by the white arrow pressing against the nerve, while the yellow arrow is pointing to the nerve itself.
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Causes of this syndrome include trauma such as a fall, acute or chronic pronation of the foot that creates excessive pressure on the inside of the ankle. Additionally, a tendonitis of the tendon that passes through the tunnel can create similar symptoms because as the tendon swells it creates excessive pressure within the confined area putting pressure on the nerve. A such as a ganglion cyst, or lipoma in the canal will also put excessive pressure on the nerve, again creating similar symptoms.
Below is an example of pronation. See how the arch has collapsed. This creates excessive tension on the inside of the ankle thus causing pressure on the nerve.
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Symptoms include burning or numbness usually on the bottom of the foot. It may be worse when standing or walking. There may also be muscle weakness of the muscles that run through the bottom of the foot. The distribution of pain or numbness is dependent on which nerve branch of the posterior tibial nerve is most affected. For that reason all of the foot or only certain parts of the foot may be affected.
Diagnosis is made by the history of the pain or numbness in the area of the distribution of the nerves on the bottom of the foot. Tenderness may be noted over the nerve just behind the ankle joint. Tapping with a finger may send sensations both forward into the foot and backward up the leg; this is known as a positive Tinel's sign. Your foot specialist should be able to determine the distribution of numbness with simple tests. There may also be muscle weakness particularly in the inability to bend your toes in a downward fashion.
Your foot specialist may also order an electromyogram (EMG) which may reveal decreased nerve conduction across the tarsal tunnel. If your doctor feels there may be a soft tissue mass, he may order an MRI.
The Kinoshita test is a pronatory "stress test". Your doctor may attempt to bend your foot upwards and at the same time pronate the foot. The foot is held in that position for ten seconds. At this point, if you have tarsal tunnel syndrome, you will start to feel the symptoms. This test was developed in 2002 and in the initial study after the patients went on to have surgery, the effectiveness of the test was confirmed in 42 out of 43 feet.
Other foot conditions may mimic the symptoms of this condition. These may include radiculopathy (nerve impingement in lower back), diabetic neuropathy, peripheral neuropathy, rheumatoid arthritis, vascular disease, Baxter's nerve (heel neuroma), plantar fasciitis, scar tissue from previous trauma or surgery, ankle edema (swelling) and possibly a growth like a ganglion cyst, or lipoma (fat tumor) in the canal.
| Condition | Primary Symptoms | Distinguishing Feature |
|---|---|---|
| Diabetic Neuropathy | Symmetrical numbness or burning in both feet. | Related to blood sugar levels; usually affects both feet in a "stocking" pattern. |
| Peripheral Neuropathy | Tingling, numbness, or "pins and needles." | Can be caused by alcoholism or vitamin deficiencies rather than physical compression. |
| Radiculopathy | Pain radiating from the lower back down to the foot. | Symptoms follow a specific nerve path (dermatome) originating from the spine. |
| Plantar Fasciitis | Sharp heel pain, especially with the first steps in the morning. | Pain is localized to the bottom of the heel; usually lacks the radiating burning of TTS. |
| Baxter's Nerve Entrapment | Chronic heel pain mimicking plantar fasciitis. | Specifically involves the first branch of the lateral plantar nerve; often misdiagnosed as a heel spur. |
| Ganglion Cyst/Lipoma | Localized swelling; pain if the mass presses on the nerve. | A physical "lump" or soft tissue mass may be visible on an MRI or felt in the canal. |
| Vascular Disease | Aching or cramping in the feet, often worse with exercise. | Related to circulation; skin may be cool to the touch or show color changes. |
An orthotic will prevent the foot from over pronating and thus relieve the pressure on the nerve. Click here for a discussion of tarsal tunnel and orthotics.
If the origin of the problem is traumatic in nature, a tarsal tunnel brace may be indicated as the brace or in many instances, a walking cast, will prevent the ankle from moving at all and will allow the inflammation in the tarsal tunnel to subside.
Adding a heel lift to the walking cast can be helpful as the slight plantarflexion that is created also helps reduce the tension and pressure on the affected nerves.
Along with the above treatments your foot specialist may also prescribe oral anti-inflammatory medicine to help reduce the inflammation.
A tarsal tunnel injection of corticosteroid may also be beneficial.
Transcutaneous nerve stimulation may be helpful as a supplemental treatment as long as the underlying cause of the tarsal tunnel is being addressed.
Other then trying an orthotic that you may purchase, there is very little you can do to remedy your symptoms. Additionally, there are no exercises which will help and actually too much exercise may aggravate your symptoms.
If none of the conservative avenues work then you must consider surgical intervention. Aside from the existing symptoms, if the pressure is not removed from the nerve, the nerve will eventually fail all together making it almost impossible to walk. The surgery itself is a soft tissue procedure whereby the ligament band pressing on the nerve is incised; the posterior tibial nerve is freed from all constricting bands.
This is an out-patient procedure. You will usually require a walking cast. However, prior to consenting to surgery other causes of these symptoms should be ruled out. These include diabetic neuropathy, a pinched nerve in the lower spine, alcoholism, rheumatoid arthritis and heavy metal neuritis just to name a few.
This is a soft tissue procedure that can be performed on an out patient basis. An incision is made just underneath the inside of the ankle bone. The laciniate ligament is a ligament that binds or holds all the vessels and nerves as they pass under the ankle joint. This ligament is incised in an effort to release the pressure that is pressing on the posterior tibial nerve which is causing the tarsal tunnel symptoms.
In addition to releasing the ligament, the area is inspected for the possibility of a growth such as a ganglion cyst which may also be causing pressure on the posterior tibial nerve. Any adhesions (fibrotic tissue attached to the nerve) is also dissected away thus freeing up the nerve.
The skin is closed. The patient may or may not be placed in a walking cast based on the preference of the surgeon.
REFERENCES
The New England Journal of Medicine
The American Journal of Medicine
Q: I am a 70-year-old male with persistent heel pain (14 months) that feels like contact pain. I’ve tried orthotics, steroids, a fracture boot, and PT with no help. One doctor diagnosed Baxter's nerve and recommended surgery; another eliminated it with a lidocaine injection and suggests RSWT. Is surgery with only a 50% success rate the right move?
A: When a diagnosis is not definitive, surgical intervention is generally not the first recommendation—especially when the success rate is cited at only 50%. Baxter's nerve entrapment and Tarsal Tunnel Syndrome are two distinct conditions located in different areas of the heel.
Recommendation: I suggest a "diagnostic experimentation" phase. By treating one condition conservatively at a time, you can isolate which one responds. If your symptoms subside with one of these targeted conservative treatments, you'll have the confidence of a final diagnosis before ever considering elective surgery.
— Marc Mitnick, DPM
Visitor Name: Lynne
Location: Cincinnati, Ohio
Hi Lynne,
The first thought that comes to mind is to give your situation some more time. Think about it. If you have a nerve entrapment as a result of your feet flattening out and putting pressure on the nerve, just by getting into an orthotic your symptoms should improve, but probably slowly. The tibial nerve is inflamed from the excess pressure, you have now removed the pressure but it takes time for the inflammation to subside.
An analogy would be an ankle sprain, you fall and twist your ankle, the ankle hurts and even though you are no longer falling, the ankle still hurts, but, gradually gets better until there is no pain.
I would suggest to you that by continual wear of your orthotics your symptoms, in theory at least should improve. Keep in mind, most people do not wear their orthotics all day long, so for example, if you come home at dinner time and kick off your shoes, you are then walking around for the next few hours pronated and re-aggravating your tarsal tunnel.
There is also a possibility that you may be able to tolerate more support than you have in your orthotics. More support, means less nerve irritation. Let your podiatrist decide on that.
Keep in mind that excess pronation is probably the most common cause of tarsal tunnel but not the only. Another cause could be a growth of some sort in the tarsal canal which will also put pressure on the nerve. I mention this because if you do not fully improve I would recommend an MRI of the tarsal tunnel canal to look for any abnormality which might explain why you still have issues.
Short of that, if after a period of time wearing your orthotics still gives you only moderate relief, speak to your podiatrist about a possible cortisone injection into the tarsal tunnel canal or even a round of oral prednisone. I also think your podiatrist has to take into account any residual effects from your right hip surgery as that may be affecting your gait as well.
At age 51 the arthritis in your midfoot is the result of being pronated, it is not the cause or precipitating factor in pronation. The accessory navicular may or may not be a precipitating factor in your flat feet.
Marc B. Mitnick, DPM
Visitor Name: Donna
Location: Downingtown, PA, United States
Question: Tarsal Tunnel Syndrome
During an examination by a nurse practitioner, a member of my family practice group, she knuckled my arch which caused instant severe pain. I have been later diagnosed with having Tarsal Tunnel Syndrome. Is it possible that her examination caused this syndrome?
RESPONSE
Hi Donna,
I doubt that knuckling your arch caused tarsal tunnel, particularly since the tarsal tunnel canal is more in the area just below the medial malleolus (the medial ankle bone) and not in your arch. There is always the possibility that the knuckling injured something directly in that area but I do not think it would be mistaken for tarsal tunnel.
Key Observation: If you have tarsal tunnel syndrome, this is something that usually takes a while to develop, in many cases from the way you walk, particularly flat-footed. In a foot that flattens out too much (over pronates), that creates a jamming on the outside of the ankle and a stretching on the inside of the ankle.
It is this stretching that puts pressure on the ligament over the nerves in the tarsal canal. This ligament then puts pressure on the nerves and you end up with the symptoms of tarsal tunnel. There are other situations that can cause tarsal tunnel, such as trauma itself to the tarsal canal or perhaps a growth of some sort that also puts pressure on the nerves as they pass through the canal.
You do not mention if you are still having severe pain where the foot was knuckled so I do not know if that warrants any discussion.
Marc Mitnick DPM
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DISCLAIMER: The purpose of this site is purely informational in nature. It is not intended to diagnose, treat or cure any medical condition. This information is not a substitute for advice from a medical professional. Please consult your healthcare provider for accurate diagnosis and treatment. The information presented here may be subject to errors and omissions.
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