Spinal stenosis is a narrowing of the spinal canal, which contains the spinal cord and nerve roots. This narrowing pinches the nerves and can cause back and leg pain. The condition can be caused by aging, being born with a small spinal canal, and a change in blood flow to the lower spine. In addition to the pain when walking, spinal stenosis also causes unusual clumsiness and a numbness or tingling in the legs. The patient may also have excessive weakness or tiredness in the legs. These symptoms often occur in other conditions described on this website, so an MRI or CAT scan may be necessary to help make the diagnosis. The doctor may also want a myelogram, which is an X-ray taken after injecting some fluid into the spine.