A herniated disc occurs when the soft, gel-like core of a cartilage disc (intervertebral disc) between the vertebrae breaks through the surrounding fibrous ring and forms a bulge toward the spinal canal. This bulge can press on nerve roots or the spinal cord, causing pain and other symptoms.

The spine is made up of vertebrae, ligaments, and intervertebral discs, which act as shock absorbers and allow movement. The discs consist of an outer fibrous ring and an inner soft core. When the fibrous ring weakens - often due to aging or injury - the soft core can be pushed out, resulting in a herniated disc.

Herniated discs most commonly occur in the lower back and, to a lesser extent, in the neck. In rare cases, they can also appear in the thoracic spine. When a herniated disc presses on a nerve, one typically experiences pain radiating into the legs, buttocks, or feet in the case of a lumbar herniation, and into the arms or hands in the case of a cervical herniation. The pain may worsen with coughing, lifting, or moving the back. Some people also experience sensory disturbances or reduced muscle strength, and in rare cases, pressure on the spinal cord can lead to difficulty walking and problems with urination or sexual function.

The symptoms of a herniated disc vary. For some, the condition can be very painful and limiting, while others may have a herniated disc without noticeable symptoms. In many cases, the symptoms disappear on their own within 3–6 months with rest and targeted exercises to relieve the back.

A herniated disc can affect people of all ages and primarily occurs due to degenerative changes in the spine resulting from aging or injury.