Why Does Your Back Hurt?
Why Identifying the Cause Is So Difficult
This is the single most important point about chronic low back pain.
Do MRI "Abnormalities" = Pain?
Not necessarily.
In a landmark 2015 study, Brinjikji and colleagues reviewed MRI scans of people with no pain across different age groups. Here is what they found:
| Age | Disc Degeneration | Disc Bulge | Disc Protrusion |
|---|---|---|---|
| 20s | 37% | 30% | 29% |
| 30s | 52% | 40% | 31% |
| 40s | 68% | 50% | 33% |
| 50s | 80% | 60% | 36% |
| 60s | 88% | 69% | 38% |
| 70s | 93% | 77% | 40% |
| 80s | 96% | 84% | 43% |
These numbers are from people who had no pain.
In other words, if you take an MRI of almost anyone over 80, you will find "disc degeneration." But 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
| Test | Limitation |
|---|---|
| Discography | Can produce pain responses even in pain-free individuals (high false-positive rate) |
| Facet joint blocks | A single block has a false-positive rate of 27–63%. "Pure" facet joint pain accounts for only about 15% of cases |
| SI joint tests | No single physical test is reliable on its own. At least 3 tests must be combined for reasonable accuracy |
| MRI | Most "abnormal" findings are normal aging. The frequency of these findings is similar in people with and without pain |
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 is not a failure of your doctor — it reflects the current limits of medical science. And crucially, 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)