Overview of the spine

The spinal column, or the vertebrae, consists of 24 separate bones along with the fused bones of the sacrum and coccyx. The vertebral column is a strong, flexible rod that protects the spinal cord, supports the head, and provides an attachment for the ribs. There are four major components of the spine: the vertebrae, joints, discs, and nerves.

  • Vertebrae: The separate bones of the vertebra link together to form a "tunnel" that protects the nerves and spinal cord. The lumbar vertebrae are under constant pressure from the weight of the upper body. The "wear and tear" of this pressure over a period of time can contribute to the development of low back pain.
  • Joints: Each pair of vertebrae is joined by 2 joints, which provide flexibility and stability within the vertebral column.
  • Discs: Discs located between the vertebrae act as "shock absorbers." Discs also function as the "glue" that holds the vertebrae together and provide flexibility within the vertebral column.
  • Nerves: At each disc level, a pair of spinal nerves exits and passes into the arms and legs. The spinal cord (which runs through the middle of the vertebrae) and the spinal nerves act as a "telephone" to allow messages, or impulses, to travel to the brain, and then to the arms and legs to control sensation and movement.

What happens to the structure of the spine as people age?

Intervertebral discs have a fiber-like ring (annulus) and a gelatin-like center (nucleus). In youth, the nucleus is about 70% fluid. As people age, the nucleus of the disc begins to "dry up," reducing the effectiveness of the shock-absorbing quality of the discs. As this protection is lost, daily activities can stress the vertebrae, causing the development of bony spurs. Bone spurs can cause the center canal that encases the spine and the side canals, which protect the nerves, to become narrowed.

What is lumbar canal stenosis?

Lumbar canal stenosis is the narrowing of the spinal canal or the tunnels through which nerves and other structures communicate with that canal. Narrowing of the spinal canal usually occurs due to changes associated with aging that decrease the size of the canal, including the movement of one of the vertebrae out of alignment.

The narrowing of the spinal canal or the side canals that protect the nerves often results in a pinching of the nerve root of the spinal cord. The nerves become increasingly irritated as the diameter of the canal becomes narrower.

What are the symptoms of lumbar canal stenosis?

The symptoms of lumbar canal stenosis include pain, numbness or weakness in the legs, groin, hips, buttocks, and lower back. Symptoms usually worsen when walking or standing and might decrease when lying down, sitting, or leaning slightly forward.

Last reviewed by a Cleveland Clinic medical professional on 07/22/2014.


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