Why does your lower back hurt? Sorting the common causes.
A dozen structures can hurt in the same place, which is why identical-sounding pain needs different plans. How to tell a disc from a joint from a muscle — and what actually needs imaging.
Most lower back pain is not one thing. It is a category — a dozen different structures that can hurt in roughly the same place, which is why two people describing identical symptoms often need completely different plans.
What causes lower back pain?
The spine is a stack of bones held together by discs, joints, ligaments and muscle. Any of those can generate pain, and the location alone rarely tells you which one.
The useful first question is not where it hurts but what makes it worse. That pattern is what separates the categories.
- Worse bending forward or sitting. Often disc-related — the cushion between two vertebrae taking load it does not like. More in herniated and bulging discs.
- Worse leaning back or standing a long time. Often the small joints at the back of the spine. See facet joint syndrome.
- Worse first thing in the morning, better once moving. Usually stiffness and guarding rather than structural damage.
- A sudden catch that locked you up. Frequently protective muscle spasm — covered in muscle spasms and cramps.
Is it a disc, a joint, or a muscle?
Age changes the odds, though not as much as people assume. Disc-driven pain is more common from the twenties through the fifties, when discs still hold enough pressure to bulge. Joint-driven pain becomes more common later, as those same discs lose height and the joints behind them take more load. Neither pattern is a rule, and plenty of sixty-year-olds have disc pain.
Muscle gets blamed for nearly everything, and it is almost always involved. But muscle is usually reacting rather than initiating.
When a joint or disc is irritated, the muscle around it tightens to protect it. That guarding is what you feel — so treating only the muscle relieves the symptom while leaving the reason for it in place. This is the single most common reason back pain keeps returning after it seemed to resolve.
Muscle tightness in the low back is usually a symptom of something else. Chasing it alone is why the same pain keeps coming back every few months.
When back pain runs down the leg
Pain that travels below the knee changes the picture. That usually means a nerve root is involved rather than just local tissue, and it is a different problem with a different timeline.
Most people call this sciatica, which is a description of the symptom rather than a diagnosis — the underlying cause might be a disc, a narrowed exit channel, or the piriformis muscle in the buttock. We break the distinctions down in sciatica explained and piriformis syndrome.
Nerve-driven pain typically settles more slowly than mechanical back pain. That is normal, not a sign that treatment is failing.
Why “it is just muscular” is usually incomplete
The reassuring version of the diagnosis is that nothing is structurally wrong and it will pass. Often true — the Mayo Clinic notes most back pain resolves within about six weeks.
The problem is what that framing leaves out. It explains the episode without explaining why you had it, which means nothing changes and the next one arrives on schedule. People who describe throwing their back out once or twice a year are rarely unlucky. They usually have a movement pattern, a work setup or a strength gap that keeps loading the same structure.
That is the part worth fixing, and it is why the plan should not end when the pain does. Our notes on lifting through low back pain cover how to keep training while that gets sorted.
What actually needs imaging
Scans are a map of structure, not of pain. Large studies of people with no back pain at all find disc bulges and degenerative changes in a substantial share of them, and the proportion climbs steadily with age. Finding one on your scan does not establish that it is the thing hurting you.
Less than people expect. Imaging early in a straightforward episode tends to find age-related changes that are present in plenty of pain-free people, which can make a mechanical problem look more alarming than it is.
What does warrant it: pain following significant trauma, progressive weakness in the leg, unexplained weight loss or fever alongside the pain, a history of cancer, or symptoms that are not improving on a reasonable timeline. Those are the cases where the exam should lead somewhere other than the treatment table.
Sudden numbness in the saddle area between the legs, loss of bowel or bladder control, or rapidly progressing weakness in both legs is a surgical emergency called cauda equina syndrome. It is rare, and it does not wait for an appointment.
How we sort it at the first visit
The 40-minute initial assessment exists because the sorting is most of the work. Movement testing shows which direction provokes and which relieves, orthopedic and neurological tests narrow whether a nerve is involved, and the history usually explains what has been reloading it.
What comes out of that is a named problem rather than a region — and the plan follows from the name. The services and pricing menu shows what each visit includes.
Track what makes it worse before your appointment. Which position, which movement, what time of day. That pattern is more diagnostically useful than a pain score, and most people have never been asked for it.
Find out which structure is actually causing it.
Frequently asked questions
- What causes lower back pain?
- Discs, the small joints at the back of the spine, ligaments and muscle can all generate pain in roughly the same place. Location alone rarely identifies the source — what makes it worse is more useful. Pain worse bending forward often points to a disc, worse leaning back often points to the facet joints, and a sudden catch is frequently protective muscle spasm.
- Is my back pain a disc or a muscle?
- Muscle is almost always involved but usually reacting rather than initiating. When a joint or disc is irritated the surrounding muscle tightens to protect it, so treating only the muscle relieves the symptom while leaving the cause in place. That is the most common reason back pain returns after seeming to resolve.
- When does back pain need an MRI?
- Less often than people expect. Imaging early in a straightforward episode tends to find age-related changes present in plenty of pain-free people. It is warranted after significant trauma, with progressive leg weakness, with unexplained weight loss or fever, with a history of cancer, or when symptoms are not improving on a reasonable timeline.
- Why does my back pain keep coming back?
- Usually because the episode was treated but the reason for it was not. People who throw their back out once or twice a year typically have a movement pattern, work setup or strength gap that keeps loading the same structure. That is the part worth addressing, and it is why a plan should not end the moment the pain does.
