The gradual wearing out of spinal discs is a natural part of aging that can often lead to a herniated disc. However, only a few people who have herniated discs have severe or troublesome symptoms.

Due to age, injury, or both, a disc's outer layer, the capsule or annulus, may dry out and develop tiny cracks. This causes the disc to bulge, break open (rupture), or break apart. Often herniated discs bulge but do not rupture or break apart.

• Bulging disc. Some of the jellylike material (nucleus) that fills the disc may leak into the cracks in the capsule. The disc may begin to bulge out from between the bones of the spine (vertebrae). It often bulges away from the spinal cord and nerve roots and therefore doesn't cause symptoms.
• Ruptured disc. The nucleus material inside the disc breaks through the capsule.
• Free fragment. Fragments of a ruptured disc may break completely free of the disc and lodge in the spinal canal, the opening in the vertebrae through which the spinal cord runs.

Any of these stages can cause pressure on a nerve root and symptoms of pain and numbness.

The cracks in the disc capsule do not repair themselves, but the pain usually fades over time. About 50% of people with a herniated disc in the low back recover within 1 month; after 6 months, most recover.¹

Often material from a herniated disc is broken down and absorbed by the body, a process called resorption. In about 2 out of 3 people, the disc herniation is at least partly gone after 6 months.²

Long-term herniated disc problems can develop.

• Pain may come and go. Periods of time when pain goes away (remission) occur less frequently.
• Long-lasting (chronic) and recurring pain can develop because of continued tissue irritation caused by the disc pressing on a nerve.
• Chronic pain syndrome can result from having ongoing pain, causing depression, anxiety, and difficulty coping with daily life.
• Symptoms caused by long-term nerve root compression include loss of agility, strength, or sensation in one or both legs and feet.

Compression of the bundle of nerve roots in the lower back (lower lumbar region) can lead to the loss of bowel, bladder, and sexual function. This rare condition, called cauda equina syndrome, requires immediate medical attention.