The spinal canal provides a protective passageway for the spinal cord and branching nerve roots. In a healthy spine, this canal maintains adequate space — typically 15-25 mm in diameter at the lumbar level. As degenerative changes accumulate over decades, bony overgrowths (osteophytes), thickened ligaments, and bulging discs gradually encroach on this space.
As the canal narrows, nerve roots become compressed against rigid bony structures. This mechanical pressure disrupts normal nerve signaling, producing the radiating pain, numbness, and muscle weakness patients experience. Even a few millimeters of narrowing can produce significant symptoms when nerves are involved.
The ligamentum flavum — a thick ligament lining the back of the spinal canal — naturally thickens and loses elasticity with age. This hypertrophy, combined with facet joint enlargement from osteoarthritis, creates a compounding effect where multiple structures simultaneously reduce the available space for neural tissue.
