Bulging Disc or Herniated Disc? How to Tell the Difference, and What Helps

Each disc between your vertebrae has a tougher outer ring surrounding a soft, gel-like center. Cleveland Clinic compares it to a jelly doughnut, which is about as good a picture as any.

A bulging disc is when that outer ring pushes out past the edges of the vertebrae above and below it, but broadly, across a big stretch of the disc. Radiologists define it as involving more than a quarter of the disc's circumference. A herniated disc is more focused: disc material pushes out through a smaller section of the ring, less than a quarter of the way around.

Put simply, a bulge is the whole disc spreading out a bit. A herniation is one spot where the inside of the disc has pushed through the wall.

Disc trouble often starts to hurt when disc material presses on or irritates a nearby nerve. When that happens in the low back, it often shows up as pain down the leg, not just in the back. In the neck, it tends to show up in the arm or near the shoulder blade.

Here's the part that surprises most people, though. Disc changes are extremely common in people who have no pain at all. A large review of imaging studies on people without back pain found disc bulges in about 30% of 20 year olds, 60% of 50 year olds, and 84% of 80 year olds. The researchers concluded that many of these findings are likely part of normal aging. So an MRI finding by itself doesn't tell the whole story. It has to match what you're actually feeling.

According to the American Academy of Orthopaedic Surgeons, most people with a herniated disc in the low back feel better within a few weeks or months without surgery, and typically, most are free of symptoms by three to four months.

The disc itself can change, too. A 2020 review of 38 studies found that about 63% of low back herniations treated without surgery got measurably smaller over time.

And one finding runs against intuition: the more a disc has pushed out, the more likely it is to shrink back. A 2015 review of low back disc studies found spontaneous regression in 96% of sequestrations and 70% of extrusions, compared to 41% of protrusions and 13% of bulges. A worse-looking MRI isn't automatically a worse outlook.

Rarely, a herniated disc can lead to a more serious problem called cauda equina syndrome. If back or leg pain comes with loss of bladder or bowel control, get emergency care right away. The American Academy of Orthopaedic Surgeons calls it a medical emergency. It's uncommon, but it's the one situation where waiting is never the right call.