The spinal cord is the part of the central nervous system, which carries information between your body and the bran.

You may have heard of people involved in a football injury, and then are unable to walk.  This is because the spinal cord was damaged during the injury, which leads to a loss of information transmission between the brain and the legs.  Without proper signal going to your legs, the legs do not function properly.

Since the signal controls the legs, it is commonly assumed that the spinal cord extends from the base of your brain down to the tail bone.

This is actually false.

The spinal cord ends in your mid-back.  Below the spinal cord, between your mid-back and your tail bone, there is a “sack” or “cavity” in which there are nerves, but no spinal cord.

The nerves that control your legs exit at the bottom of your spinal cord (in your mid-back), and travel down this sack to your lower back, where they exit the “spinal canal” and extend down your legs.

So an injury to the spinal cord will disrupt the signals to these nerves extending down your legs.  If the nerves are not receiving proper information from your brain, they will will not function properly.

Hence, damage to syour spinal cord (anywhere between the mid-back and your neck) can directly affect the function of your legs.