Sciatica due to herniated disc.... most of this are not truth

there are other causes of sciatica such as:

1. Sacroiliitis

Sacroiliitis is an inflammation of your sacroiliac joint. That's the joint where your hip meets the spine. Inflammation caused by trauma or just plain arthritis can give you sciatica-like symptoms. Sometimes an injection of an anesthetic and an anti-inflammatory medication can take away the pain.

2. Lumbar Facet Joint Syndrome

Lumbar Facet Joint Syndrome is pain that comes from the joints of your back causing not only back discomfort, but also it can give you sciatica-like symptoms. The facet joint is like any other joint of your body.

3. Piriformis Syndrome

Piriformis Syndrome is simply pain caused by the piriformis muscle that may be in spasm, inflamed, or irritated. This muscle is in your buttock and lies right on top of the sciatic nerve as it exits the spine and goes down your leg. As you can imagine, if this muscle is having a problem, it will cause pressure on the nerve, giving you the sciatica-like symptoms.

4. Iliolumbar Syndrome

Iliolumbar Syndrome is simply inflammation or a tear of the iliolumbar ligament. This ligament extends from the spine to the iliac crest, which is the back of your pelvis.

5. Lumbar Spinal Stenosis

Last, but not least, Spinal Stenosis, which is narrowing of the spinal canal, can cause sciatica-like symptoms. The narrowing can be caused by disc problems as well as arthritis of the spine.
Source:spineuniverse