Spinal stenosis is a disease affecting the nerves exiting the spinal canal.
Nerves leave the spine through little windows termed neuroforamen.
When the neuroforamen are reduced in size due to surrounding debris, the nerves react to the pressure by swelling. As the window closes on the nerve the associated pain may become excruciating and debilitating. Spinal stenosis may also cause numbness, weakness, burning sensations, tingling, and pins and needles in the involved extremity, such as the leg. Some patients with spinal stenosis may find the pain eases when bending forward or sitting. This may happen because bending forward creates more vertebral space, which may temporarily relieve nerve compression.