Ask the Experts: Foot Numbness

I am a 2-4 mile runner 5 days/wk and I have had a problem for years. After about 20 mins of running, my left foot (and sometimes both) fall asleep. Doctors are puzzled…does this happen to anyone else?

-Carrie

While foot numbness is a symptom of several different medical conditions, including diabetes, vitamin B12 deficiency and even lead poisoning, the condition in runners is often due to some sort of nerve compression. The most common of these is called Morton’s Neuroma. It’s caused by a compression of the nerve between the third and fourth toe. Numbness will typically start on the outside of the third toe and inside of the fourth toe, but can often spread throughout the whole foot. Over time, the nerve thickens with scar tissue. The condition is more common in women than in men  – possibly due to wearing high heels.

If you’re experiencing Morton’s Neuroma, the first thing to try is a pair of shoes with a wide toe box. You’ll want to avoid shoes that jam your toes into the front. So, look for something loose enough that you can wiggle your toes a bit, but not so loose that your feet slip in them and your toes forcibly slide into the front of the shoe. Another trick is additional padding under the forefoot. This will help spread the bones gently so they don’t compress the nerve.

Numbness in the foot can also be caused by tarsal tunnel syndrome. This is the foot/ankle equivalent of carpal tunnel syndrome. Three tendons, an artery, veins and the tibial nerve make their way through the “tarsal tunnel” in the ankle. When the tibial nerve becomes compressed, numbness and pain can ensue. This condition is somewhat more serious than Morton’s Neuroma because the symptoms of numbness and pain during exercise can progress to numbness and pain while at rest.

Before you panic, look at your shoe laces. If you’re getting numbness in your feet that starts at the ankle, loosen your laces or try a different lacing technique. You just might be compressing the nerve by tying your shoes too tightly. If that fails to relieve the symptoms, see your doctor. I’m just a running coach and I’m not medically trained. Good luck!