The causes of lower back pain range from simple muscle strains that heal in a few days to serious conditions requiring prompt medical care. Lower back pain is one of the most common health complaints worldwide; health authorities including the NIH estimate that roughly 80% of adults will experience it at some point in their lives, and it is a leading cause of disability and missed work.
Knowing the different causes of lower back pain, and how to distinguish ordinary muscular pain from more concerning conditions, helps you decide when self-care is appropriate and when to see a doctor. This guide breaks down the most common causes, the red flags that warrant urgent evaluation, and what each type of back pain typically feels like. It is general educational information, not medical advice; when in doubt, have your symptoms evaluated by a clinician.
Call 911 or go to the emergency room now if back pain comes with any of these warning signs:
- New loss of bladder or bowel control (incontinence, or being unable to urinate), numbness around the groin, buttocks, or inner thighs (saddle numbness), or new weakness in both legs — these can signal cauda equina syndrome, a surgical emergency where delay can cause permanent nerve damage.
- A sudden, severe, “tearing” or ripping pain in the back or abdomen, especially with faintness — this can signal a life-threatening aortic emergency.
- Back pain after major trauma (a fall from height or a serious crash).
- Back pain with a high fever, or in someone using IV drugs, which can indicate a spinal infection.
Muscular and Mechanical Causes
The majority of lower back pain episodes are mechanical in nature, meaning they involve the muscles, ligaments, discs, or joints of the spine without dangerous nerve compression or systemic disease. Most improve substantially within a few weeks.
Muscle strain or sprain: The most common cause of acute lower back pain. It occurs when muscles or ligaments in the lower back are stretched, torn, or overloaded. Common triggers include lifting heavy objects awkwardly, sudden twisting, prolonged poor posture, and “weekend warrior” bursts of activity. Pain is typically localized, worsens with movement, and eases with rest. Most muscle strains improve within a few weeks.
Degenerative disc changes: As intervertebral discs lose hydration and height with age, they cushion the vertebrae less. This is a normal part of aging rather than a “disease,” and disc degeneration shows up on imaging in most adults over 40, including many with no pain at all. When it does cause symptoms, it typically produces a dull, chronic ache that can worsen with prolonged sitting and ease with movement.
Facet joint dysfunction: The facet joints connect the vertebrae and allow spinal movement. Inflammation or arthritis in these joints can cause localized lower back pain that worsens with extension (arching backward) and rotation. It is often worst in the morning and improves with gentle activity.
Myofascial pain syndrome: Tight bands and trigger points in the muscles of the lower back and surrounding areas can cause chronic, aching pain. It is often related to posture, repetitive movements, or stress, and tends to respond to physical therapy, targeted exercise, and stretching.
Disc-Related Causes
Intervertebral disc problems are a significant category of lower back pain causes.
Herniated disc (slipped disc): When the soft inner core of a disc pushes through a tear in the outer layer, it can press on a nearby nerve. A herniated disc in the lumbar spine can cause lower back pain along with radiating pain, numbness, or tingling down one or both legs (sciatica). According to the Mayo Clinic, most herniated discs improve with conservative treatment over several weeks. For more on sciatic nerve pain, see our guide on symptoms of sciatica.
Bulging disc: Less severe than a herniation, a bulging disc extends beyond its normal boundary while the inner core stays contained. Bulging discs are extremely common on MRI and often cause no symptoms. When they do, it is usually a dull ache that may worsen with sitting or bending forward.
Disc extrusion or sequestration: When herniated disc material breaks free from the disc, it can cause more significant nerve compression and more severe symptoms. This is less common but may require surgical evaluation if it causes progressive neurological deficits.
Nerve-Related Causes
When nerves in the lower back are compressed or irritated, pain often radiates beyond the back itself.
Sciatica: Not a diagnosis in itself but a symptom of nerve irritation, typically from a herniated disc or bone spur. Sciatica causes pain that radiates from the lower back through the buttock and down the back of one leg, sometimes with numbness, tingling, or weakness. It is common, affecting a substantial share of people at some point in life.
Spinal stenosis: Narrowing of the spinal canal, usually from age-related changes, that compresses the spinal cord or nerve roots. Lumbar spinal stenosis is most common in older adults and typically causes back and leg pain that worsens with walking or standing and improves with sitting or bending forward (neurogenic claudication).
Cauda equina syndrome: A rare but serious emergency in which the bundle of nerves at the base of the spinal cord is severely compressed. Symptoms include severe lower back pain, saddle anesthesia (numbness in the groin and inner thighs), bladder or bowel dysfunction, and progressive leg weakness. This requires emergency evaluation and usually urgent surgery to prevent permanent damage. If you have these symptoms, call 911 or go to the emergency room immediately — do not wait to see whether they improve.
Spondylolisthesis: One vertebra slips forward over the one below it, potentially compressing nerves. It can cause lower back pain and leg pain, particularly with activity, and may result from a stress fracture (more common in young athletes) or degenerative changes (more common in older adults).
Inflammatory and Systemic Causes
Some causes of lower back pain arise from inflammatory conditions or systemic disease rather than mechanical strain.
Ankylosing spondylitis: A chronic inflammatory condition primarily affecting the spine and sacroiliac joints. It often begins in younger adults and causes morning stiffness lasting more than 30 minutes, pain that improves with exercise but worsens with rest, and gradual loss of spinal mobility. It affects a small percentage of the population and benefits from early diagnosis.
Sacroiliac (SI) joint dysfunction: Inflammation or abnormal movement of the sacroiliac joints, where the spine meets the pelvis, can cause deep, aching lower back and buttock pain. It is common during pregnancy, after trauma, and in people with a leg-length difference.
Kidney stones or kidney infection: Pain from the kidneys can mimic lower back pain but is typically felt on one side (flank pain) and may radiate to the groin. It is often accompanied by urinary symptoms (frequent or painful urination, blood in the urine) or fever, which warrant prompt care.
Abdominal aortic aneurysm: A rare but potentially fatal cause of lower back or abdominal pain, more common in older adults with a history of smoking or high blood pressure. The pain can be deep, pulsating, and constant. A sudden, severe tearing pain, especially with dizziness or fainting, is a medical emergency — call 911.
When Lower Back Pain Is Something More Serious
While most lower back pain is benign, certain red flags warrant medical evaluation, and some warrant emergency care. The Mayo Clinic, Cleveland Clinic, and NIH describe warning signs that include:
- Loss of bladder or bowel control, or inability to urinate (emergency)
- Numbness in the groin or inner thighs (saddle anesthesia) (emergency)
- Progressive leg weakness or foot drop (urgent)
- Severe pain after a fall, accident, or major trauma (urgent)
- A sudden tearing back or abdominal pain, especially with faintness (emergency)
- Pain accompanied by unexplained weight loss
- Back pain with fever not explained by another illness (possible infection)
- Pain that is worse at night or does not improve with rest
- New back pain in someone with a history of cancer
- Back pain in someone using IV drugs (infection risk)
- New, unexplained back pain at the extremes of age without prior back problems
These red flags may point to conditions such as cauda equina syndrome, spinal infection, spinal fracture, or cancer that require prompt diagnosis and treatment. When they are present, do not rely on self-care — seek care right away.
Diagnostic Approaches
Most uncomplicated lower back pain does not require imaging in the first four to six weeks unless red flags are present. The American College of Physicians notes that early imaging for routine back pain does not improve outcomes and can lead to unnecessary tests and treatments.
When imaging is warranted, options include:
- X-rays: Show bone alignment, fractures, and degenerative changes, but do not visualize soft tissues like discs or nerves.
- MRI: The most detailed test for evaluating discs, nerves, the spinal cord, and soft tissue.
- CT scan: Provides detailed bone imaging and can be useful when MRI is unavailable or contraindicated.
- Nerve conduction studies/EMG: Evaluate nerve function when nerve root compression (radiculopathy) is suspected.
- Blood tests: May be ordered to check for infection, inflammatory conditions, or other systemic causes.
For additional health condition information, visit our conditions guide.
Conservative Care for Ordinary Back Pain
For the common muscular or mechanical episode with no red flags, the evidence supports a conservative approach. The American College of Physicians recommends starting with non-drug measures such as staying active, applying heat, and trying physical therapy, massage, or targeted exercise, and using over-the-counter anti-inflammatory medication only as needed and as directed. Prolonged bed rest is discouraged because it tends to slow recovery. Most acute episodes improve substantially within a few weeks, and gradually returning to normal activity is usually the goal. If your pain is severe, persistent, or accompanied by any warning sign, check in with a clinician rather than pushing through.
Frequently Asked Questions
How do I know if my lower back pain is muscular?
Muscular lower back pain typically feels like a dull ache or a sharp pain localized to the lower back that worsens with movement, eases with rest, and does not radiate far into the legs. It often follows a specific event (lifting, twisting) or a period of overuse. If pain radiates past the knee, involves numbness or tingling, or comes with weakness, it may involve nerve compression rather than just a muscle strain, and is worth evaluating.
When should I worry about lower back pain?
Worry, and seek prompt care, if back pain comes with bowel or bladder problems, saddle numbness, progressive leg weakness, unexplained weight loss, or fever, or if it follows a significant injury. Any of the emergency signs in the red-flag box above (including loss of bladder or bowel control or a sudden tearing pain) means calling 911 or going to the ER. Also see a clinician if pain persists beyond about six weeks despite self-care.
Can lower back pain be a sign of cancer?
In rare cases, yes. Cancers that can cause back pain include spinal tumors, cancer that has spread to the spine (especially from breast, lung, prostate, or kidney cancers), and multiple myeloma. Cancer-related back pain tends to be persistent, progressive, worse at night, and accompanied by other symptoms such as unexplained weight loss or fatigue. If you have a history of cancer and develop new back pain, see your doctor promptly.
Should I rest or stay active with lower back pain?
Current evidence strongly supports staying gently active over bed rest for most lower back pain. The NIH and American College of Physicians recommend avoiding prolonged bed rest, which can actually worsen outcomes. Gentle activity, walking, and a gradual return to normal routines tend to lead to faster recovery than extended rest.
What is the fastest way to relieve lower back pain?
For acute muscular lower back pain, relief often comes from a combination of gentle activity, heat or ice, careful stretching, and over-the-counter anti-inflammatory medication such as ibuprofen or naproxen used as directed (check with a pharmacist or clinician if you have other health conditions). Most acute episodes improve significantly within a few weeks with these measures. If pain is severe or accompanied by any red flag, seek care instead of self-treating.
Listen to Your Body and Know When to Seek Help
Understanding the causes of lower back pain helps you respond appropriately. Most episodes are muscular, self-limiting, and respond well to conservative care. However, recognizing red flags and seeking timely evaluation when symptoms suggest something more serious can prevent complications and ensure you get the right treatment. If your lower back pain does not improve within four to six weeks, or if you experience any of the warning signs above, schedule an appointment with your healthcare provider — and for emergency signs, do not wait.
The TL;DR: Most lower back pain is muscular or mechanical and improves within a few weeks with gentle activity, heat or ice, and over-the-counter pain relief — imaging usually is not needed early on. Watch for red flags: new loss of bladder or bowel control, saddle numbness, or weakness in both legs can mean cauda equina syndrome (call 911), and a sudden tearing pain can signal an aortic emergency (call 911). Back pain with fever, major trauma, a cancer history, unexplained weight loss, or IV drug use also needs prompt care.
This article is general education, not medical advice, and does not replace evaluation by a clinician. Call 911 for emergency warning signs.
Sources
- Mayo Clinic — Back pain: symptoms, causes, and when to see a doctor
- Cleveland Clinic — Lower back pain and cauda equina syndrome
- MedlinePlus / NINDS (U.S. National Institutes of Health) — Low back pain
- American College of Physicians — Clinical guideline on noninvasive treatment of low back pain
- NIAMS (U.S. National Institutes of Health) — Back pain information