Q. I'm 40 years old, and last year I ruptured a disc in my spine. My doctor said it was at the L5-S1 level. What exactly does that mean?

I had a limp and my left ankle reflex didn't work properly. I was treated with bed rest but no surgery. My limp and ankle reflex returned to normal.

Lately, I've developed a problem in my left leg. The outer part of my foot is numb and my left knee feels stiff. I wear shoes all the time now, because walking barefoot gives me a stretching pain in the back of my left leg. Could these problems be related to my ruptured disc?

A. Yes. It sounds like the same disc is putting pressure on the nerve that runs down your leg.

Discs are cushions of cartilage that act like shock absorbers between the bones of the spine. When a disc "ruptures," it bulges out from between the spinal bones, where it can pinch one of the major nerves as it exits the spine in your lower back.

You have 33 spinal bones, each numbered for its location: 7 cervical in the neck, 12 thoracic in the chest, 5 lumbar in the lower back, 5 sacral bones fused together to form the sacrum of your pelvis and 4 tiny bones fused together to form the end of your tailbone, or coccyx. A ruptured disc at L5-S1 is between the fifth lumbar bone and first sacral bone, one of the two most common spots for a ruptured disc. (The other is just above it at L4-L5).

A ruptured disc at L5-S1 puts pressure on the first sacral nerve as it exits the spine to travel down your leg. Damage to it leads to a certain set of symptoms: Pain in your buttocks that shoots down the back of your leg, numbness in the back of your leg and along the outside of your foot, a decrease in your ankle reflex (the jerking of your ankle in response to your Achilles tendon being hit) and weakness of flexing your foot and toes downward, a motion you need to do, for example, when you walk up stairs.

Because different nerves exit at different levels of your spine, your doctor can usually pinpoint the site of a ruptured disc by the characteristic set of symptoms it causes.

The reason you're more comfortable wearing shoes is that the heels give the back of your feet a little lift and lessen the pull on the sacral nerve. You're walking a fine line, so to speak, because the little extra pull you get from walking barefoot is enough to stretch the nerve over the ruptured disc and trigger your pain.

Because you're having some of these symptoms, it's likely that your ruptured disc is giving you trouble again. I recommend seeing your doctor for further treatment. If you show signs of significant injury to your nerve, you may need surgery to prevent further damage.

Jay Siwek, a family physician from Georgetown University, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington.

Consultation is a health education column and is not a substitute for medical advice from your physician.

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