Herniated Disk Diagnosis

Medically Reviewed by Tyler Wheeler, MD on September 22, 2022
3 min read

Back pain can sneak up on you when you least expect it. One minute you're sitting comfortably in front of the TV, and the next you try to stand up, and -- ouch! -- a sharp pain radiates through your lower back.

Could you have a slipped or herniated disk? You might.

The adult spine is made up of 24 bones called vertebrae. Some of the vertebrae are cushioned by soft disks made of a jellylike substance. These disks allow you to move your spine around and bend over.

But if a disk between two vertebrae starts slipping out of place, it can irritate the surrounding nerves and cause extreme pain. The condition is called a slipped, ruptured, or herniated disk.

One sign may be where the pain is. Although herniated disks can happen in any part of your spine, they are most common in the lower part of your backbone (the lumbar spine), just above your hips. The pain may spread from your back to your buttocks, thighs, and even to your calves.

Discomfort from a herniated disk usually gets worse when you're being active and lessens when you're resting. Even coughing, sneezing, and sitting can worsen your symptoms because they put pressure on pinched nerves. A herniated disk also can give you a feeling of tingling or numbness. The affected part of your back may also feel weak.

Age also plays a role. As you get older, your disks tend to break down and lose their cushioning. That makes a herniated disk more likely.

The best way to tell if you have a herniated disk is to see your doctor. They’ll likely do a physical exam to find the source of your pain. This usually is the only test you’ll need to confirm a diagnosis. Your doctor will check your back for sore or painful spots. They may ask you to lie on your back and lift or move your legs in certain ways. If you feel pain, it’s likely a herniated disk.

They may also check:

  • Your reflexes at the knee and ankle
  • Your leg strength
  • How you walk on your heels and toes
  • Whether you can feel light touches or vibrations

If your doctor wants to rule out other sources of your pain, or pinpoint specific nerves that are aggravated, they may do further testing, including:

  • X-rays. While a standard X-ray can't show if you have a herniated disk, it can show your doctor the outline of your spine and rule out whether your pain is caused by something else, such as a fracture or tumor.
  • Myelogram. This test uses dye injected into your spinal fluid, and an X-ray to locate the pressure on the spinal cord.
  • CT scan. A CT (or CAT) scan takes several X-rays from different angles and combines them to create images of your spinal cord and the structures surrounding it.
  • MRI. An MRI uses radio waves, a magnetic field, and a computer to create detailed 3D images of the spinal cord and surrounding areas. MRI images can locate the position of the herniated disk, look inside it, and also determine which nerves are affected.
  • Electromyogram (EMG). Your doctor might use these tests to see if any nerves are damaged or compressed. The EMG test uses a device to detect the tiny amount of electricity muscle cells make when they're stimulated by nerves connected to them. A needle electrode put into a muscle records its electrical activity and looks for anything that isn’t as it should be.
  • Nerve conduction studies (NCS) are often done at the same time as the EMG. In this test, the nerves are stimulated with tiny electrical impulses by an electrode at one point on the body while other electrodes detect the impulses at a different point. The time it takes for the electrical impulses to travel between electrodes lets your doctor know whether there is nerve damage.