Why Tarsal Tunnel Syndrome Is So Often Missed in Diabetic Patients

KEY TAKEAWAYS:

• In people with diabetes, tarsal tunnel syndrome is frequently mistaken for diabetic peripheral neuropathy because the two conditions share symptoms like burning, tingling, and numbness in the feet. 
• The difference matters: neuropathy is often managed with medication alone, while a compressed nerve in the tarsal tunnel may be relieved surgically. 
• Recognizing the signs of nerve compression—and getting evaluated by a peripheral nerve surgeon—can be the difference between masking symptoms and addressing their root cause.

If you have diabetes and your feet burn, tingle, or feel numb, you have probably been told it is diabetic neuropathy. But that might not be the full story. Tarsal tunnel syndrome, a pinched nerve at the inner side of the ankle, can cause nearly identical symptoms. 

In people with diabetes, tarsal tunnel syndrome can be an overlooked source of foot pain in people. The distinction is easy to miss and important to get right, because the two problems are treated in very different ways.

Dr. Eric H. Williams is a board-certified plastic and reconstructive surgeon with fellowship training in peripheral nerve surgery who treats patients from the Baltimore area, across the country, and internationally as well.  A large part of his work involves nerve decompression for diabetic neuropathy, and a recurring theme among the people he sees is a compressed nerve that was hiding in plain sight behind a diagnosis of “neuropathy”. 

Here, Dr. Williams explains how the two conditions differ and how surgery may be able to provide relief. 

What Is Tarsal Tunnel Syndrome?

Tarsal tunnel syndrome is a compression neuropathy—a condition in which a nerve gets squeezed inside a narrow space. Here, the nerve is the posterior tibial nerve, which passes through a tight channel of tissue on the inner side of the ankle called the tarsal tunnel. When the nerve is pinched there, it can cause the nerve to stop functioning correctly. When this occurs, the nerve can then send pain, tingling, burning, numbness, or electric-shock sensations into the sole of the foot and toes. It is essentially the foot’s version of carpal tunnel syndrome in the wrist, where a nerve is compressed as it travels through a tunnel.

The posterior tibial nerve is a complex nerve that sends signals to both the skin as well as to muscles. As the nerve travels downstream in the foot, it branches into four smaller nerves—the medial plantar, lateral plantar, medial calcaneal, and inferior calcaneal nerves—that fan out to supply sensation to different parts of the sole and heel. The nerve also helps control the muscles that flex the ankle and curl the toes.

Because each branch travels through its own smaller, tighter tunnel as it leaves the ankle, compression can happen at more than one point. If the nerve is not decompressed at each of these appropriate levels, the patient may not see the results that they were hoping for. This is why education into the appropriate method of decompressing these nerves is critically important.  

Compression is rarely an all-or-nothing event. In the early stages, a nerve under mild pressure may cause only occasional tingling or a vague ache, and many people adjust their footwear or activity and move on. Over time, though, steady pressure can interfere with the nerve’s blood supply and its ability to carry signals, and symptoms that once came and went can become constant. That slow progression is part of why the condition slips under the radar for so long—especially when a neuropathy diagnosis already seems to explain everything.

Why Is Tarsal Tunnel Syndrome So Often Missed in People With Diabetes?

The short answer is that diabetes both mimics and causes nerve compression at the same time. Three factors make this condition especially easy to overlook.

Overlapping Symptoms

Diabetic peripheral neuropathy and tarsal tunnel syndrome produce strikingly similar complaints: burning feet, pins and needles, numbness, and shooting pain. Because up to half of people with diabetes develop peripheral neuropathy, a clinician seeing those symptoms in a patient with diabetes will reasonably think of neuropathy first. The trouble is that a pinched nerve can produce the very same picture, so the diagnosis that fits the most patients is not always the one that fits this patient.  In addition, many of these patients will have both situations.   

Diabetes Tightens the Tarsal Tunnel

Diabetes does not only damage nerves from the inside; it also changes the tissue around them. High blood sugar drives a process called glycosylation, in which excess sugar molecules bind to proteins and make the fibrous tunnel around the nerve stiffer and tighter. At the same time, the nerve itself tends to swell, partly because of fluid retention and inflammation. A larger nerve inside a smaller tunnel is a recipe for compression, which is one reason nerve entrapment is more common, not less, in people with diabetes. Reduced blood flow from diabetes can also leave the nerve more vulnerable to pressure, because it is already working with a thinner margin of oxygen and nutrients.

Neuropathy Becomes the Default Explanation

Once neuropathy is on the chart, it tends to absorb every new symptom. Foot pain that is actually coming from a trapped nerve gets folded into the neuropathy diagnosis and managed with medication. Some patients spend years being told nothing more can be done, when the real problem or at least a major part of the problem is a mechanical one that was never investigated.

The same pattern shows up with other foot complaints, including plantar fasciitis that won’t go away despite standard treatment, which may also be truly from a nerve compression. 

How Can You Tell Nerve Compression From Diabetic Neuropathy?

No single test settles the question, but several findings point toward a treatable compression rather than diffuse nerve damage. The first is a positive Tinel sign—tingling or an electric jolt that shoots into the foot when the nerve is gently tapped at the ankle. It is the same “funny bone” feeling you get when you bump your elbow. You can even check for a positive Tinel sign at home.

Diffuse, symmetric numbness in both feet is more typical of classic neuropathy. Pain that follows one nerve, flares with activity, and responds to a targeted block is more suggestive of compression. In fact, when a patient with diabetes and nerve pain has a positive Tinel sign, there is roughly an 85% chance that a surgically treatable nerve compression is part of the picture—even in people who have been told for years that they simply have to live with neuropathy.  

One huge problem in patients with diabetes is that they may also have symptoms in the top of the foot.  The tibial nerve in the tarsal tunnel does not supply the top of the foot, but the common peroneal nerve does.  The common peroneal nerve wraps around the knee and gets pinched by the exact same mechanisms as described above for the tibial nerve in the tarsal tunnel.  When you add the common peroneal nerve and the tibial nerve together, you have what looks like the classic description of the “stocking distribution” of diabetic neuropathy.   

Why Does the Diagnosis Change Your Treatment Options?

This is where getting the answer right pays off. Neuropathy from widespread nerve damage is usually managed by first trying to treat the underlying cause of the problem if and when possible.  For instance, keep your blood sugar as normal as possible. When that does not work, then symptoms are managed with medications that try to dull the symptoms; they can help, but they do not repair the underlying nerve. 

A nerve that is trapped in the tarsal tunnel (or any other tunnel for that matter) is a different situation. If too much pressure is the problem, relieving that pressure is a logical solution. Surgical decompression opens the tunnel and frees the nerve so it has the chance to recover.

Dr. Williams approaches this by releasing all four branches of the posterior tibial nerve rather than only the main nerve alone. Research he took part in with surgeons at Johns Hopkins suggests that freeing the medial and lateral plantar nerves lowers the pressure inside these smaller tunnels and can help restore blood flow to the nerve.  Prior to his retirement, Dr. A. Lee Dellon spent nearly 20 years redefining how these nerves should be decompressed, leading to substantially improved outcomes when compared to historical controls.  Dr. Williams has been performing these procedures since 2007.  

Results vary from person to person, and not everyone is a candidate, but many people experience meaningful, lasting relief once the compression is addressed.

Of course, even surgery has its limits. Decompression treats the mechanical part of the problem—the squeezing—so the nerve can try to recover and carry signals more normally again. It does not reverse the metabolic damage that high blood sugar causes throughout the body. Steady blood sugar control remains essential before and after any procedure. The goal is to remove a fixable source of pain, not to cure diabetes or replace the rest of a person’s care.

Who Is a Good Candidate for Nerve Decompression?

Surgery is not the right answer for everyone, and a thorough evaluation comes first. In general, people tend to be better candidates for nerve decompression when they have reasonably controlled blood sugar (an A1C under 8.5), a body mass index under 50, healthy blood flow to the feet with a palpable pulse, and no medical conditions that would make anesthesia unsafe. These factors give the nerve the best chance to heal once the pressure is relieved. 

Someone who does not meet every benchmark today may still become a candidate after working with their care team to improve blood sugar control or circulation, which is one more reason an evaluation is worthwhile. If there are steps you can take to become a stronger candidate for surgery, Dr. Williams can explain your next steps.

In appropriately selected patients, we would expect about 80-85% to achieve good to excellent resolution of pain, improved sensation, and improved balance.  This has been shown consistently in many prospective studies from the US and abroad. There is growing data that supports the effectiveness of nerve decompression surgery in appropriately evaluated patients with suspected overlying nerve compressions in the setting of well-controlled diabetes. 

What Does Recovery From Tarsal Tunnel Surgery Look Like?

Recovery is gradual, and knowing the general timeline helps set realistic expectations. Most patients can walk with crutches right after surgery and stay off the foot for about 24 hours, then bear weight as tolerated with the crutches. Keeping the leg elevated as much as possible in the first days helps control swelling. 

The foot is wrapped in a soft dressing for roughly one week, and sutures usually come out after about three weeks. From there, the focus shifts to gentle movement—such as walking on even surfaces or using an exercise bike—so the nerve can glide freely as it heals. 

How soon someone returns to work depends on the job: desk work may resume quickly, while physically demanding work can call for about four weeks off. Dr. Williams will review what to expect during your recovery prior to scheduling your procedure.

When Should You Consider Seeing a Peripheral Nerve Surgeon?

It is worth discussing your symptoms with a peripheral nerve surgeon if your foot pain follows a single nerve, worsens with activity, or has not improved with medication alone. An evaluation can determine whether a compressed nerve is contributing to pain that has been blamed entirely on neuropathy. Because more than one nerve can be compressed in the same leg, symptoms in different parts of the foot do not rule out a treatable cause—they may point to several.

For many people with diabetes, years of being told to simply live with burning, tingling feet turn out to have a mechanical cause that medication was never going to fix. Getting evaluated does not replace daily blood sugar control and routine foot care, but distinguishing tarsal tunnel syndrome from diabetic neuropathy can open a door to relief that had seemed closed.