Definition of Herniated disk:

A herniated (slipped) disk occurs when all or part of a disk in the spine is forced through a weakened part of the disk. This places pressure on nearby nerves.

See also:

• Acute low back pain
• Chronic low back pain
• Sciatica

Causes, incidence, and risk factors:

The bones (vertebrae) of the spinal column protect nerves that come out of the brain and travel down your back to form the spinal cord. Nerve roots are large nerves that branch out from the spinal cord and leave your spinal column between each vertebrae.

The spinal bones are separated by disks. These disks cushion the spinal column and put space between your vertebrae. The disks allow movement between the vertebrae, which lets you bend and reach.

• These disks may move out of place (herniate) or break open (rupture) from injury or strain. When this happens, there may be pressure on the spinal nerves. This can lead to pain, numbness, or weakness.
• The lower back (lumbar area) of the spine is the most common area for a slipped disk. The neck (cervical) disks are affected a small percentage of the time. The upper-to-mid-back (thoracic) disks are rarely involved.

Radiculopathy is any disease that affects the spinal nerve roots. A herniated disk is one cause of radiculopathy.

Slipped disks occur more often in middle-aged and older men, usually after strenuous activity. Other risk factors include conditions present at birth (congenital) that affect the size of the lumbar spinal canal.