Nerves branch out from the spinal cord to energize the muscles of the body. The nerves travel to your body through smaller openings in the vertebrae called foramina. The aging process can cause a deterioration in the elasticity of the disks. Flexibility can be diminished. Sudden movements or violent shocks can cause the disk to herniate.
Herniation is akin to a tire blowing out.
In the chyart below, the green area is the nerve, the blue area is the disk, while the brown area is the vertebrae. Further deterioration in the disk can cause the vertebrae above and below the damaged disk to touch, and develop bone spurs on the vertebrae and foramina. This causes a narrowing of the spinal canal and foramina, which in turn causes pressure on the nerves emanating from the affected area. This filling of the openings with bone spurs is called spinal stenosis. This unfortunately advances the process of pain, weakness, numbness, and lost coordination and can dramatically reduce the quality of life.