Many people who suffer from low back pain also have a sharp pain, numbness, and tingling going down the leg.  Those symptoms going down the leg are called sciatica.

Disc Herniations

The most common cause of sciatica is herniated discs.  When a portion of a disc herniates, it can pinch surrounding nerves and cause pain and sensations wherever that nerve travels.  When a nerve is pinched in the low back, it can cause irritation of the sciatic nerve which runs from the low back to the feet.

Sacroiliac Joint Dysfunction and Piriformis Syndrome

If there's an imbalance in the pelvis, it can shift the sacrum which is connected to the piriformis muscle.  This subtle shift can cause inflammation of the muscles and surrounding tissues, which can then place pressure on the sciatic nerve.

Spinal Stenosis

Stenosis means there is a narrowing of the spaces where the spinal cord or spinal nerves run through.  Spinal stenosis is usually seen with people over the age of 50 because it's associated with arthritis and disc degeneration, aka degenerative disc disease.  As the discs degenerate, the space in between vertebra diminishes, and this causes narrowing of openings.  As these openings narrow, they can pinch nerves and cause sciatica.

Other

Spondylolisthesis - this is slippage of a vertebra that can cause back pain.  In addition to back pain, people with this condition may also complain of leg pain.

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