low back

What is the lumbar spine and how does it normally work?

The human spine is part of the body’s skeletal system that provides balance and stability, protects the spinal cord, and allows you to turn, stretch and bend.

A normal spine allows you to move about freely and bend with flexibility. Your low back, or lumbar spine, is made up of five bones (vertebrae) which are numbered L1 to L5 and are stacked on top of each other to form a column (see Fig. 1). Each lumbar vertebra has a hole for the spinal cord which contains nerves that carry signals from your brain to the rest of your body. Below the lumbar spine is the sacrum.

The spine’s vertebrae (or bones) absorb the impact from walking, climbing or jumping. The spinal cord runs through the spinal canal at the back of the spine and is protected by the vertebrae (see Fig. 2).

There are also discs between the vertebrae which act as shock absorbers to cushion impact and to keep the distance between the vertebral bodies. Each disc has a thick outer layer (annulus) that surrounds a soft gel-like center (nucleus).

A spinal joint consists of two vertebrae in the front of the spine separated by a flexible disc and two facet joints in the back of the spine. See Fig. 1 for a diagram of the lumbar spine and a spinal joint.

Smaller nerves branch out from the spinal cord at each level and lead to specific areas of the body. See Fig. 2 for a diagram of the lumbar spinal cord and the nerve branches at each level.