Tarsal tunnel syndrome

What is tarsal tunnel syndrome?

The tarsal tunnel is a narrow passage behind and below the inner ankle bone (the medial malleolus). Its roof is a band of tissue called the flexor retinaculum. Running through it are the tibial nerve, an artery and veins, and several tendons that move the foot and toes. In or near the tunnel, the tibial nerve divides into branches that supply feeling to the heel and sole and control small muscles in the foot.^[1,2]

When something narrows the tunnel or stretches the nerve, the nerve can become irritated — much as the median nerve does in carpal tunnel syndrome at the wrist. This is sometimes called posterior tarsal tunnel syndrome, to distinguish it from a different condition on the top of the foot (see nerve entrapment in the foot and ankle).

Symptoms

• burning, tingling, “pins and needles” or numbness in the sole, heel or toes
• shooting or electric pain along the inner ankle and into the arch
• symptoms that build with prolonged standing, walking or exercise, and sometimes at night
• tenderness behind the inner ankle; tapping over the nerve may send tingling into the foot
• in longer-standing cases, weakness or wasting of the small muscles in the foot (less common)

Tarsal tunnel syndrome usually affects one foot. Symmetrical symptoms in both feet more often point to peripheral neuropathy or a problem in the lower back, although the conditions can overlap.^[1]

What causes it?

Anything that takes up space in the tunnel or puts the nerve under tension can contribute:^[1,2,4]

• Space-occupying lesions such as ganglion cysts, enlarged veins, fatty lumps, swollen tendon sheaths, bone spurs or extra muscles
• Foot position — for example a flattened arch or a heel that tilts outward, which can stretch the nerve
• Injury — ankle sprains or fractures, and scar tissue after an injury or surgery
• Medical conditions that make nerves more vulnerable or cause swelling, such as diabetes, inflammatory arthritis or thyroid disease

In many people, no single cause is found.^[1]

How it’s evaluated

Because several conditions can mimic tarsal tunnel syndrome, evaluation is careful and methodical.

• History: where the symptoms are, when they occur, what makes them better or worse, previous injuries or surgery, and other health conditions.
• Examination: sensation and strength in the foot, tenderness and tapping along the nerve, foot alignment, gait and footwear, circulation, and a check for signs that the problem may be coming from the back, hip or knee.
• Conditions to distinguish include plantar fasciitis, Baxter’s nerve entrapment, peripheral neuropathy, arthritis and pinched nerves in the lower back.

Testing. MRI or ultrasound can show a cyst or other structure pressing on the nerve. Nerve-conduction studies and EMG can support the diagnosis, but they may be normal in some people who have the condition, so results are interpreted together with the examination.^[1,7] Nerve studies are usually performed by another specialist; when they’re needed, we coordinate the testing and review the results with you.

Treatment options

Treatment is matched to the cause and to how much the symptoms affect your life.

Non-surgical care

• Reducing pressure and tension on the nerve: supportive footwear, orthotics to improve heel and arch alignment, or bracing.
• Activity changes: a temporary break from the activities that provoke symptoms.
• Physical therapy: exercises for strength and flexibility, and gentle nerve-gliding movements.
• Medication: medicines for nerve pain may be helpful and are coordinated with your primary care physician or other clinicians.
• Injection: a corticosteroid injection may be considered in selected cases.
• Addressing contributing conditions, such as blood-sugar control or inflammatory arthritis.^[3]

Non-surgical care is often effective for nerve entrapments of the foot and ankle, and surgery is generally reserved for symptoms that don’t respond.^[6] The evidence for any single treatment is limited, so the plan is reviewed as you go.^[2]

Surgery

If symptoms persist despite several months of well-tried non-surgical care — or if a cyst or other structure is clearly compressing the nerve — surgery to release the tarsal tunnel may be discussed. The operation opens the flexor retinaculum to relieve pressure on the nerve and its branches, and removes any compressing structure.^[4] Learn more about nerve decompression surgery.

Results vary. Outcomes tend to be more predictable when a specific cause, such as a cyst, is found and removed, and less predictable when no clear cause is identified or symptoms have been present for a long time.^[2,4]

Recovery and realistic expectations

• Non-surgical care usually takes weeks to months to show its full effect.
• After surgery, there is typically a period of protected weight-bearing and swelling. Nerve symptoms often improve gradually over months; numbness may recover more slowly than pain, and some symptoms may remain.
• Not everyone improves, and repeat surgery for persistent symptoms is more complex. That is one reason the diagnosis is confirmed carefully before surgery is recommended.

When to seek care

Consider an evaluation if burning, tingling or numbness in your sole lasts more than a few weeks, keeps you from standing or walking comfortably, or is getting worse. If you have diabetes, have new foot symptoms checked promptly.