Herniated Disc (often referred to as a Slipped Disc)
A herniated disc is a frequent cause of mild or moderate low back or leg pain. Soft flexible discs separate the bones in the spine. The discs, which have a rigid outside rim and a soft, gel-like centre, act as shock absorbers and protect the spinal cord. Activity, stress, or a mechanical problem in the spine can cause a disc to bulge and become misshapen. The damaged or bulging disc may pinch or irritate a nerve root, causing pain.
The sciatic nerve, composed of several lumbar nerve roots, is one of the nerves most likely to become irritated, usually by a herniated disc. Each of the major branches of sciatic nerve travels through the pelvis and deep in the buttocks, then down the hip and along the back of the thigh to the foot. The pain of sciatica ranges from a mild tingling to a sharp ache severe enough to cause immobility.
Lumbar spinal stenosis
Degeneration of the spine also can result in lumbar spinal stenosis (LSS). This disease involves a narrowing of the canal that houses the spinal cord and nerve roots. A narrowed spinal canal may compress nerve roots in the lower back, resulting in pain and weakness in the legs and a dull pain in the lower back. Patients often find relief by sitting or standing in a hunched over position, as if leaning on a shopping cart. Symptoms of LSS usually do not occur until after the age of 50.