Why Does Your Back Hurt?

1. Back Pain Has Many Suspects — Not Just One

The lower back contains several structures that can each generate pain. In most cases, more than one is involved at the same time.

1. Discs — The Spine's Shock Absorbers

Involved in an estimated 26–42% of chronic low back pain cases

Spinal discs sit between each pair of vertebrae and absorb impact. Over time, the outer wall of the disc (the annulus) can develop small tears. When nerves and blood vessels grow into these tears, the disc itself becomes a source of pain.

Typical pain: A deep, dull ache in the center of the lower back. Tends to worsen with prolonged sitting and improve when you stand up.

Key fact: Disc degeneration appears on MRI in 37% of 20-year-olds and 96% of 80-year-olds, even when they have no pain at all (Brinjikji 2015).

2. Facet Joints — The Spine's Small Hinges

Involved in an estimated 15–45% of chronic low back pain cases

Facet joints are pairs of small joints at the back of the spine that guide and limit movement. Like any joint, their cartilage can wear down over time, leading to arthritis.

Typical pain: Pain on one or both sides of the lower back. May spread to the buttocks or upper thighs. Tends to worsen with bending backward or twisting.

Important: Even when imaging shows facet joint changes, those changes may not be causing the pain. About 10% of people in their 30s already show facet changes on imaging, and the frequency of these changes is similar in people with and without pain (Borenstein 2004).

3. Sacroiliac (SI) Joint — Where the Spine Meets the Pelvis

Involved in an estimated 10–30% of chronic low back pain cases

The SI joints connect the base of the spine (sacrum) to the pelvis (ilium) on each side. They transfer the weight of the upper body to the legs. Childbirth, leg length differences, prior spinal surgery, and inflammatory conditions can all contribute to SI joint pain.

Typical pain: Pain in one buttock that you can point to with a finger. May spread to the groin area.

4. Muscles and Fascia — The Back's Support System

Involved in an estimated 30–85% of pain clinic patients

Muscle injuries, overuse, and prolonged poor posture can produce "trigger points": tight, tender knots within muscles. These can cause local pain and also refer pain to other areas of the body.

Typical pain: Sore, tight spots that hurt when pressed, with pain that seems to spread or radiate. Tends to worsen with stress and fatigue.

5. Central Sensitization — When the Volume Gets Turned Up

Central sensitization is a fairly new idea in pain science.

When pain persists for weeks or months, the nervous system (the spinal cord and brain) can shift into a heightened state. It's as if someone has turned up the volume on your pain without you noticing.

When this happens:

• Stimuli that shouldn't hurt (light touch, gentle pressure) start to cause pain
• Mild pain signals get amplified into severe pain
• Pain persists even after the original tissue has healed

This is not "all in your head." It is a real, measurable change in how the nervous system works. The International Association for the Study of Pain (IASP) has given this type of pain its own name: nociplastic pain, meaning pain that comes from altered processing in the nervous system itself.

Poor sleep, chronic stress, anxiety, and depression can all worsen central sensitization (Nijs 2018).

6. Spinal Stenosis — A Narrowing That Can Also Cause Back Pain

Spinal stenosis (another topic covered in detail on this site) is best known for leg symptoms such as numbness, tingling, and difficulty walking. But the changes that cause stenosis (enlarged facet joints, thickened ligaments, and degenerating discs) can also cause lower back pain themselves.

For more on spinal stenosis → What Is Spinal Stenosis?

2. Why Identifying the Cause Is So Difficult

This is the most important point about chronic low back pain.

Do MRI "Abnormalities" = Pain?

Not necessarily.

In a 2015 study, Brinjikji and colleagues reviewed MRI scans of people with no pain in different age groups. They found:

These numbers are from people who had no pain.

An MRI of almost anyone over 80 will show "disc degeneration." This is a normal part of aging, like gray hair, not a disease.

Dr. Brinjikji himself concluded:

"Many imaging-based degenerative features are likely part of normal aging and unassociated with pain."

The Limits of Diagnostic Tests

Multiple Pain Generators at Once

In practice, most people with chronic low back pain have more than one pain source active at the same time:

• Disc problems + facet joint arthritis + muscle tension
• SI joint pain + central sensitization
• Structural changes + psychological factors (anxiety, depression)

This reflects the current limits of medical science, not a failure by your doctor. Not being able to pinpoint a single cause does not mean your pain is "not real." Your pain is real.

"It was not possible to identify a subgroup of chronic low back pain patients for whom spinal fusion was reliably effective." — Willems 2013 (comprehensive review of prognostic tests for spinal fusion)

3. So What Can Be Done?

"If the cause can't be identified, does that mean nothing can help?" No.

Because chronic low back pain usually involves several factors, approaches that address several of them at once tend to be the ones that help.

Approaches Supported by Evidence

1. Appropriate exercise therapy: Exercises matched to the type of pain have been reported to improve outcomes (Long 2008)
2. Pain education: Understanding how pain works has been reported to reduce pain intensity on its own
3. Psychological approaches: Cognitive behavioral therapy and mindfulness have been shown to help (Cherkin 2016, JAMA)
4. Medication management: Not a cure-all, but some medications can provide relief as part of a broader plan
5. Spinal cord stimulation (SCS): An option for patients who have not responded to conservative treatment. Like any surgical procedure, SCS carries risks including infection, lead migration, and the possibility that it may not provide adequate relief. When appropriate, it has been reported to help reduce pain in selected patients.

The Key Takeaway

An MRI finding alone is not a reason for surgery.

A large clinical trial with 11 years of follow-up found that spinal fusion for non-specific chronic low back pain did not produce a clinically meaningful difference compared to structured rehabilitation (Mannion 2013).

4. Summary and Next Steps

Summary

• Chronic low back pain has 6 main pain generators: discs, facet joints, SI joints, muscles, central sensitization, and spinal stenosis
• In more than 85% of chronic low back pain cases, no single cause can be identified
• MRI "abnormalities" are usually normal aging: the same changes found in 96% of pain-free 80-year-olds
• Because multiple sources are involved, combined, multi-modal treatment approaches tend to work better than targeting one structure
• "MRI abnormality → surgery" is not supported by the evidence

Questions to Ask Your Doctor

Some questions to consider at your next appointment:

• "Which pain source do you think is most likely involved in my case?"
• "Are my MRI findings likely the cause of my pain, or are they age-related changes?"
• "Could central sensitization be playing a role in my pain?"
• "If multiple sources are involved, what combination of treatments would you recommend?"

References

1. Brinjikji W et al. "Systematic literature review of imaging features of spinal degeneration in asymptomatic populations." AJNR Am J Neuroradiol. 2015;36(4):811-6.
2. Brinjikji W et al. "MRI Findings of Disc Degeneration are More Prevalent in Adults with Low Back Pain than in Asymptomatic Controls." AJNR Am J Neuroradiol. 2015;36(12):2394-9.
3. Urits I et al. "Low Back Pain, a Comprehensive Review." Curr Pain Headache Rep. 2019;23(3):23.
4. Allegri M et al. "Mechanisms of low back pain: a guide for diagnosis and therapy." F1000Res. 2016;5.
5. Willems P. "Decision making in surgical treatment of chronic low back pain." Acta Orthop Suppl. 2013;84(349):1-35.
6. Schuttert I et al. "The Definition, Assessment, and Prevalence of Central Sensitisation in Patients with Chronic Low Back Pain." J Clin Med. 2021;10(24):5931.
7. Manchikanti L et al. "Comprehensive Evidence-Based Guidelines for Facet Joint Interventions." Pain Physician. 2020;23(3S):S1-S127.
8. Cohen SP et al. "Sacroiliac joint pain: a comprehensive review." Expert Rev Neurother. 2013;13(1):99-116.
9. Borenstein D. "Does osteoarthritis of the lumbar spine cause chronic low back pain?" Curr Pain Headache Rep. 2004;8(6):512-7.
10. Mannion AF et al. "Comparison of spinal fusion and nonoperative treatment in patients with chronic low back pain: long-term follow-up of three randomized controlled trials." Spine J. 2013;13(11):1438-48.

Next Steps

• Warning Signs — Red Flags You Should Not Ignore
• Exercise Therapy — Why Movement Is an Effective Treatment
• Tests and Diagnosis — What Examinations Are Needed
• About Surgery — An Honest Look at the Evidence for Spinal Fusion