Spinal stenosis is a narrowing in the spinal canal. Constriction of the spinal nerves can produce pain that goes down one or both of the arms or legs, depending on the location of the stenosis. Malfunction of the nerves can cause numbness In the arms or legs, or weakness in muscles served by the affected spinal nerves.
Your doctor can confirm the diagnosis with imaging techniques such as MRI or CT scan.
The interesting part of this condition to me is the tremendous advances in surgical techniques that have taken place in the past decade. Many surgeries are now done through an endoscope, which limits the surgical disruption in the area. There is even a needle guided procedure to remove part of the ligament that is causing compression of the nerve.
Depending on the exact problem, small amounts of bone or other tissues can be removed, especially if the exact site of compression has been identified. If the extent of compression is more extensive, increasing amounts of bone is removed from the lamina (bony arches), facets , or nerve outlets (foramina) to give the nerves more room.
If there is slippage of the vertebra, a fusion is sometimes done. My understanding is that fusion is becoming less common. That being said, the Cloward procedure in the neck, with its approach from the front, is still sometimes used with neck pain.
Pain in the neck or back without any associated nerve malfunction is often best treated with physical therapy, steroid injections, or other conservative methods.
In my opinion spinal surgery is best done by trained neurosurgeons, who are familiar with minimally invasive surgery.