At every level of the spine the nerves will exit through a small canal. This canal is called the foramen or foraminal canal. Foraminal stenosis is a narrowing of this canal.
Constriction of the nerve roots leaving the spine in the foraminal canal is typically caused by bone spurs, a herniated or bulging disc, arthritis or ligament thickening. Foraminal Stenosis can also be caused by enlargement of a joint (the uncinate process) in the spinal canal.
Foraminal Stenosis can produce a type of pain called radicular pain which is pain that radiates into the lower extremity (the thigh, calf, and may spread to the foot) directly along the course of a specific spinal nerve root. It is often deep, steady and reproducible with certain activities such as sitting or walking, and follows the involved area of distribution of the leg covered by the specific nerve. It can be accompanied by numbness and tingling, muscle weakness and loss of specific reflexes.
The most common cause of radicular pain is sciatica (pain that radiates along the sciatic nerve - down the back of the thigh and calf into the foot).Radicular pain is secondary to compression, inflammation and/or injury to a spinal nerve root.