A bulging spinal disc occurs when the disc's soft, jelly-like centre (nucleus) is squeezed against the disc's outer covering, weakening and stretching that covering. As a disc bulges out from between the neighbouring bones (vertebrae), it can irritate or press on nerves that travel to the legs or arms and can cause numbness, weakness, or pain. But often, bulging discs don't cause any symptoms.

Normally, spinal discs absorb shock and provide flexibility within the spine. With age, spinal discs break down. They become drier, less flexible, and more easily damaged through wear and tear or sudden injury. People who smoke cigarettes are at increased risk of disc deterioration.

In most cases, symptoms of a bulging disc can be managed with non-surgical treatment and will go away over time. In a few cases, surgery is needed.