Do You Need an MRI for Back Pain? What It Can and Can't Show
Updated: 4 days ago
Most people with back pain don't need an MRI right away. Many cases get better on their own or with simple care like activity changes and physical therapy. An MRI is most useful when there are warning signs, when pain doesn't improve after several weeks of treatment, or when a doctor needs detailed pictures to plan care such as an injection or surgery.
This guide explains when an MRI makes sense for back pain, what it can and can't show, and what to expect if your doctor orders one.
Back pain is very common
Back pain is one of the most common reasons people see a doctor. It can feel like stiffness, a dull ache, sharp pain, or pain that travels down a leg. It can be mild or severe and can get in the way of work, sleep, and daily life.
The first step is usually a visit with your doctor. They'll ask about your symptoms and history and do a physical exam. For many people, that's enough to start treatment without any imaging.
How MRI shows the spine
MRI uses a strong magnet and radio waves to make detailed pictures. It does not use radiation. That makes it different from X-rays and CT scans.
MRI is especially good at showing soft tissue. In the spine, that includes:
The discs between the bones
The spinal cord and nerve roots
Ligaments and muscles
Fluid and swelling
The bones themselves, including swelling inside the bone
To learn more about how spine scans work, see our guide to spine MRIs.
When you may need an MRI for back pain
Warning signs
Doctors call certain symptoms "red flags." These may point to a more serious problem and can be a reason to image the spine sooner. They include:
New numbness or weakness in the legs
Loss of bladder or bowel control, or numbness in the groin or inner thighs
Back pain after a major injury, such as a fall or car accident
A history of cancer with new back pain
Fever or other signs of infection along with back pain
Unexplained weight loss with back pain
Loss of bladder or bowel control, or numbness in the groin area, can be a medical emergency. Get care right away if this happens.
Pain that doesn't get better
If your pain hasn't improved after several weeks of treatment, your doctor may order an MRI to look for a cause.
Planning treatment
An MRI can help a doctor plan a procedure such as a spinal injection or surgery. It shows exactly where a disc or nerve problem is.
If your back pain started after a car accident, our article on spinal injuries in car accidents explains how MRI is used.
What an MRI can show
A lumbar (low back) MRI can show:
Herniated or bulging discs: when the soft center of a disc pushes out
Pinched nerves: a disc or bone spur pressing on a nerve root
Spinal stenosis: narrowing of the space around the spinal cord or nerves
Disc wear: discs that have lost water and height over time
Arthritis: changes in the small joints of the spine
Fractures and bone swelling: including some fractures that X-ray may miss
Infection or tumors: less common, but important to find
What an MRI can't show
MRI gives detailed pictures, but it has limits.
It can't tell exactly where pain comes from
Many adults have disc bulges, disc wear, or arthritis on MRI and no back pain at all. These changes are a normal part of aging for many people. So a finding on an MRI isn't always the cause of your pain. Your doctor matches what the scan shows with your symptoms and exam.
It can't show muscle strain well
Many cases of back pain come from strained muscles or irritated soft tissue. These often don't show up clearly on an MRI.
It can't show how your spine moves
MRI images are taken while you lie still. Pain that happens only with certain movements may not have a clear cause on the scan.
Incidental findings
An MRI may show things unrelated to your current pain. These are called incidental findings. Most are harmless, but they can cause worry or lead to more tests. Talk with your doctor about what each finding means for you.
MRI vs. X-ray and CT for back pain
Test | Good for | Limits |
X-ray | Bone alignment, fractures, arthritis | Doesn't show discs or nerves |
CT | Detailed bone pictures | Limited soft tissue detail; uses radiation |
MRI | Discs, nerves, spinal cord, soft tissue, and bone | Takes longer; you must stay still |
Learn more in our guide to MRI vs. CT vs. X-ray.
MRI safety
MRI is safe for most people. The main things to know about are:
Metal and devices: pacemakers, cochlear implants, some surgical clips, and other devices may not be safe in the scanner. Many newer devices are designed to be safe for MRI under certain conditions. Always tell the team about any implant or device.
Contrast dye: most back MRIs don't need contrast. If contrast is used, you'll be asked about allergies and kidney health first. Serious reactions are rare.
For more, read the essential guide to MRI safety.
What to expect during a back MRI
You'll lie on your back on a padded table that slides into the scanner. Pads may be placed under your knees to help you stay comfortable. The machine makes loud knocking sounds, so you'll get earplugs or headphones. You'll need to stay still while the pictures are taken.
The scan is painless. You can go back to normal activities right after. A board-certified radiologist reads the images and sends a report to your doctor.
Frequently asked questions
Should I get an MRI for lower back pain?
Not always. Many cases improve without imaging. Your doctor may order one if you have warning signs, if your pain doesn't improve with treatment, or if they're planning a procedure.
Can an MRI show a pinched nerve?
Yes. MRI can show a disc or bone spur pressing on a nerve root. Your doctor will check whether that matches your symptoms.
Will an MRI show a muscle strain in my back?
Usually not clearly. Muscle strains are a common cause of back pain but often don't show up well on MRI.
What if my MRI shows a bulging disc?
Disc bulges are common, even in people without pain. Your doctor will decide whether it's likely related to your symptoms. Our guide to understanding spine MRI terms explains common report words.
How long does a back MRI take?
It depends on the exam. At Millenium MRI, most patients are in and out in about 35 minutes.
Related reading
Schedule an MRI at Millenium MRI
Millenium MRI has centers in Ocala, Largo, and Tamarac, Florida, and in North Little Rock, Springdale, Jonesboro, and Marion, Arkansas. Our board-certified radiologists and ARRT-certified technologists perform spine MRIs, and results are usually sent to your doctor within 24 hours. Same-day appointments are often available. We accept most insurance plans, workers' compensation, personal injury cases, and self-pay. Hours are Monday through Friday, 9am to 5pm.
This article is for general information and is not medical advice. Talk with your doctor about your specific situation.
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