Tarsal Tunnel Syndrome: Causes Of and Treatment For This Common Foot Condition

Tarsal tunnel syndrome is a common foot condition that can be quite disabling. Similar to carpal tunnel syndrome in the wrists, this painful disease can cause numbness, burning, tingling, and shooting pain to the bottom of the foot and heel. Pain is felt usually with activity or standing, but can also be present while resting if the inflammation is severe enough. An intense pain is usually noted on the side of the foot and ankle, extending to the heel. In many cases the pain is so specific to the heel that one can be tricked into thinking there is a problem with the bottom of the heel only. The toes can also feel numb or tingly, and an intense burning can also be felt in the ball of the foot. This condition usually only affects one foot at a time, as similar symptoms in both feet at the same time may represent a problem away from the feet themselves. By definition, it is a nerve condition (a 'pinched' nerve if you will). Many other conditions can cause symptoms consistent with nerve disease in the foot, but few have similar findings as tarsal tunnel syndrome.



The problem lies within a structure called the tarsal tunnel. This part of the foot is located under and just forward to the inside part of the ankle. A tight fibrous retinaculum (a type of ligament) crosses over the top of this area, while other tissue forms the walls and bottom of this 'tunnel'. Through this tunnel a large bundle passes, consisting of a nerve, and artery, and a vein. These structures supply the sensation and circulation of the bottom of the foot respectively. Tightness of the tissues surrounding this bundle can occur for a variety of reasons. Flat feet seem to be implicated as a cause in many of these cases, as the flattening of the foot places added stress to the ligament covering the tunnel, which results in pressure on the nerve. Also, any mass present in that small space, like a tendon cyst or even varicose branch off of the vein that runs alongside the nerve, can cause pressure against the nerve. There may even be enlargement of a small muscle located at the front of this area that can cause the symptoms. Regardless of the cause, once pressure develops against the nerve the outer fibers will become damaged. The vein and artery are not affected similarly, as they are flexible enough to withstand some pressure and the circulation to the foot is therefore not affected. Over time, the nerve damage will increase and pain will develop. This process is similar to what happens when one falls asleep on their arm, and then wakes up with the arm feeling 'asleep'. Often mistaken for poor circulation, this 'sleepy' feeling in the arm simply represents excessive pressure on one of the nerves in the arm, and not cut-off circulation. This is a common misperception among many people who have healthy circulation and mistake a nerve problem for poor blood flow. Release of the nerve pressure allows the arm to 'wake-up' after a short while. Now, imagine this process slowly occurring in the foot around the clock. The resulting pain and discomfort will be very similar, but relief will not come by simply changing sleeping positions.



This condition is easily diagnosed by pushing on the tarsal tunnel and finding pain and tingling. Tapping firmly on the nerve can bring about a shooting or tingling up or down the foot, indicating a diseased nerve in various stages of a self-healing attempt. A normal nerve will not have this same effect. X-rays show nothing for this condition, but ultrasound or an MRI can show if there is inflammation or a mass occupying space in or around the tarsal tunnel. A special nerve test called a nerve conduction velocity study can measure the amount of time an electrical signal takes to travel down the nerve. Measured in a fraction of a second, this time will be normal above the tarsal tunnel and delayed below it. A specific extension to the foot has to be ordered by your physician in order to assess the tarsal tunnel, as this test does not usually include the foot nerves when it is typically ordered for other nerve conditions in the legs.



Treatment for this condition requires numerous steps, and ultimately may result in a need for surgery to release the internal pressure on the nerve. Non-surgical treatment can be effective in the early stages of the disease. This includes combinations of anti-inflammatory medications, cortisone-like steroid injections near the nerve to reduce inflammation, icing, orthotics and leg braces to take away foot motion in an effort to reduce strain of the ligament, and physical therapy to release any scar tissue or adhesions around the nerve tissue. Anti-inflammatory medications will reduce the body's overall state of inflammation, helping to limit some of the pain associated with this condition. The more direct application of steroid medication via an injection will act even more specifically on the inflamed tissue around the nerve. Several injections may be need to achieve effectiveness. Icing will likewise reduce inflammation at the tarsal tunnel when applied directly over the area, temporarily reducing the inflammation. By using a prescription shoe insert (orthotic), the abnormal stress from over flattening of the feet placed on the ligament restricting the tarsal tunnel can be effectively controlled in the long term. More intensive support may be needed to restrict the motion of the foot all together, and this can come in the form of stiff ankle braces, immobilizing boots, or even a cast. Finally, physical therapy techniques including manipulation of the foot tissue and ultrasound therapy can be helpful in restoring a more normal state to the tarsal tunnel. Unfortunately, if the condition has progressed further or if non-surgical therapy is ineffective, surgery to free up the tarsal tunnel from any tightness is required. This procedure is usually quite effective at relieving the condition, although scar tissue from the surgery can result in additional problems in uncommon cases. Essentially, an incision is made along the inside of the foot near the ankle, and the ligament restricting the nerve is released. The nerve is identified, and its course through the tarsal tunnel as well as the course of all its branches are freed from any restrictive tissue. The ligament is left unrepaired to allow for a more expanded scar-type tissue to fill in the gap, essentially creating a deeper space for the nerve to sit in. The skin is then sewn and a supportive dressing and brace applied to be used during the recovery period. Support in an orthotic after the surgery is helpful in preventing the condition from reoccurring, as are supportive shoes.



This highly painful and disabling condition is best treated early, as waiting to seek care can prolong the nerve damage and result in a more difficult treatment course. Timely medical attention by a foot and ankle specialist (podiatrist) when numbness, burning, or tingling develops on the bottom of the foot (or anywhere on the foot for that matter) can be the key to a successful recovery. This condition rarely ever resolves on its own.





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D r. Kilberg provides compassionate and complete foot and ankle care to adults and children in the Indianapolis area. He is board certified by the American Board of Podiatric Surgery, and is a member of the American Podiatric Medical Association. He enjoys providing comprehensive foot health information to the online community to help the public better understand their feet. Visit his practice website at www.inpodiatrygroup.com