A bulging spinal disc occurs when the disc's soft, jellylike center (nucleus) is squeezed into cracks in the disc's outer covering, weakening and stretching that covering. As a disc bulges out from between the neighboring bones (vertebrae), it can press on nerves that travel to the legs or arms and can cause numbness, weakness, or pain.

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. Injury and prolonged overuse or misuse can speed the formation of tiny tears in a disc's capsule. People who smoke cigarettes are at increased risk of disc deterioration.

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