What Causes Lower Back Pain?

Why Is Lower Back Pain So Common?

The lumbar spine supports much of the body's weight while also allowing movement and protecting important nerves. It is therefore exposed to considerable mechanical forces during everyday activities such as walking, bending, lifting and twisting.

Lower back pain is very common. An episode may develop suddenly, perhaps following an awkward movement or activity, or symptoms may develop more gradually without an obvious injury.

For many people there is no single identifiable cause. This is sometimes described as non-specific lower back pain.

What Structures Can Cause Lower Back Pain?

Several structures within and around the lumbar spine are capable of contributing to pain. These include:

• muscles and other soft tissues surrounding the spine
• intervertebral discs
• facet joints
• vertebrae
• ligaments
• nerve roots
• the sacroiliac region and other structures around the pelvis

However, identifying the exact structure responsible for an individual's pain can be difficult. Symptoms, examination findings and imaging results need to be interpreted together rather than assuming that every abnormality visible on a scan is responsible for the pain.

Common Causes of Lower Back Pain

There are several conditions and mechanisms that can be associated with lower back pain.

Muscular and Soft-Tissue Pain

Back pain can occur following strain or irritation of the muscles and soft tissues around the lumbar spine. This may follow lifting, unusual physical activity, repetitive movement or a sudden awkward movement, although there is not always an obvious triggering event.

Symptoms may include localised aching, stiffness and discomfort with certain movements. Many episodes improve with time and appropriate activity.

Age-Related Changes in the Spine

The structures of the spine naturally change as we get older. Intervertebral discs can lose some of their water content and height, while joints and other structures can develop degenerative changes.

These changes are common and do not necessarily cause symptoms. This is one reason why MRI findings must be interpreted alongside a patient's history and clinical examination.

Disc-Related Problems

Intervertebral discs sit between the vertebrae and help distribute loads through the spine.

Changes within a disc can sometimes be associated with lower back pain. A disc may also bulge or prolapse (sometimes called a slipped or herniated disc). If disc material irritates or compresses a nearby nerve root, symptoms may extend beyond the back and into the leg.

This can result in sciatica or leg pain, which may be accompanied by tingling, altered sensation, numbness or weakness.

Facet Joint Changes

Facet joints are small joints at the back of the spine that help guide and control movement.

Like other joints, they can develop degenerative changes over time. In some individuals, these joints may contribute to localised lower back pain and stiffness.

Lumbar Spinal Stenosis

Lumbar spinal stenosis describes narrowing within the spinal canal or around the spaces through which spinal nerves travel.

It is more commonly associated with symptoms affecting the legs than isolated lower back pain. Some people experience pain, heaviness, numbness or weakness in the legs when standing or walking, with symptoms improving when sitting or bending forwards.

Spinal stenosis is more common as people get older and can develop as a consequence of several age-related changes within the lumbar spine.

Spondylolisthesis

Spondylolisthesis occurs when one vertebra moves forwards relative to the vertebra below it.

Some people with spondylolisthesis have no symptoms, while others may experience lower back pain or symptoms caused by narrowing or irritation around the spinal nerves.

Spinal Fractures

A fracture of a vertebra can cause back pain. Fractures may follow significant trauma, but vertebral compression fractures can also occur following relatively minor trauma in people whose bones have been weakened by osteoporosis.

New severe back pain following an accident or injury requires appropriate medical assessment.

Inflammatory Conditions

Some forms of back pain are associated with inflammatory conditions rather than the more common mechanical or degenerative causes.

The pattern of symptoms can differ from typical mechanical back pain. A clinician may consider an inflammatory cause based on factors including the person's age, symptom history, stiffness, other medical conditions and examination findings.

Can Lower Back Pain Have a Serious Cause?

Most lower back pain is not caused by a serious underlying condition. However, a small proportion of people can have back pain associated with conditions that require more urgent investigation or treatment.

These can include:

• spinal fracture
• infection
• cancer affecting the spine
• significant neurological compression
• cauda equina syndrome
• certain inflammatory conditions

A medical assessment is therefore not based simply on how painful the back feels. The pattern of symptoms, how they developed, associated symptoms, medical history and examination findings can all be important.

What Is the Difference Between Lower Back Pain and Sciatica?

Lower back pain and sciatica can occur together, but they are not the same condition.

Lower back pain is primarily felt in the lumbar region. Sciatica occurs when a nerve supplying the leg becomes irritated or compressed and typically causes symptoms extending into the buttock and leg.

Sciatica may cause:

• sharp, burning or shooting leg pain
• pins and needles or tingling
• numbness or altered sensation
• weakness in part of the leg or foot

Some people with sciatica also experience back pain, while others find that their leg symptoms are much more significant than their back pain.

Read more about leg pain and sciatica.

Does the Location of Back Pain Identify the Cause?

Not necessarily.

The location and behaviour of pain provide useful clinical information, but pain alone does not always identify a particular damaged structure.

For example, pain may be central or predominantly affect one side of the lower back. It may sometimes spread towards the buttocks or upper leg without necessarily representing sciatica.

A specialist assessment therefore considers the overall pattern rather than relying on one symptom in isolation.

Why Can MRI Findings Be Misleading?

MRI scanning provides detailed images of the discs, nerves and other soft tissues within the lumbar spine. It can be extremely useful when there is an appropriate clinical reason for imaging.

However, structural and age-related changes can be visible on scans in people who have few or no symptoms. Finding a disc bulge or degenerative change on an MRI does not automatically establish that it is responsible for somebody's pain.

For this reason, an MRI should be interpreted in the context of the person's symptoms and clinical findings.

Our separate guide explains when an MRI scan may be considered for lower back pain.

How Is the Cause of Lower Back Pain Assessed?

Assessment usually begins with a detailed medical history and clinical examination.

A spinal specialist may ask about:

• when the pain started
• whether symptoms developed suddenly or gradually
• the location and nature of the pain
• activities or positions that make symptoms better or worse
• whether pain travels into the buttock or leg
• numbness, tingling or weakness
• previous episodes of back pain
• previous treatment
• general health and relevant medical history
• any symptoms that could indicate a more serious underlying condition

The examination may assess spinal movement, strength, sensation, reflexes and other neurological functions where appropriate.

Investigations are then considered when they are likely to provide clinically useful information or influence management.

Do I Need an MRI Scan for Lower Back Pain?

Not everyone with lower back pain requires an MRI scan.

In many cases, particularly when symptoms have only recently developed and there are no concerning features, imaging may not alter treatment.

An MRI may be considered when symptoms persist, when there are neurological symptoms, when a particular spinal condition is suspected, or when the result could influence treatment decisions.

Read our detailed guide: MRI Scans for Lower Back Pain: When Are They Needed?

Does Lower Back Pain Mean I Need Surgery?

No. Most people with lower back pain do not require spinal surgery.

Treatment depends upon the underlying problem, duration and severity of symptoms, how much the symptoms affect everyday life, examination findings and, where relevant, imaging results.

Depending upon the diagnosis and individual circumstances, non-surgical management may include advice about activity, rehabilitation or physiotherapy, medication and other selected treatments.

Surgery is generally considered only when there is an identifiable condition for which an operation may offer meaningful benefit and the potential benefits justify the risks.

Read more: When Does Back Pain Require Surgery?

When Should I Seek Medical Advice About Lower Back Pain?

Medical advice should be considered when back pain is persistent, worsening, significantly affecting normal activities or accompanied by other symptoms that require investigation.

You should also seek medical advice if you are concerned about your symptoms or if the pattern of pain has changed significantly.

Some symptoms require urgent medical assessment. Seek urgent or emergency medical help if back pain is associated with new problems controlling or passing urine or stools, loss of sensation around the genitals or anus, significant or worsening weakness or numbness affecting both legs, or symptoms following a serious accident.

These symptoms can have several causes, but may indicate significant compression of the nerves in the lower spine, including the rare condition cauda equina syndrome, and should not be assessed solely using online information.

Frequently Asked Questions About Lower Back Pain

What is the most common cause of lower back pain?

There is often no single identifiable anatomical cause. Lower back pain can involve muscles, joints, discs and other spinal structures, and many episodes are described as non-specific lower back pain. The exact cause is not always apparent even after assessment.

Can a slipped disc cause lower back pain?

Yes. A prolapsed or herniated disc can be associated with back pain. If the disc irritates or compresses a spinal nerve root, it can also cause pain, tingling, numbness or weakness extending into the leg.

Can arthritis cause lower back pain?

Degenerative changes can affect the joints and other structures within the lumbar spine as people get older. These changes may contribute to symptoms in some people, but similar changes can also be present in people without significant pain.

Why does my back hurt if my scan is normal?

Pain cannot always be explained by a clearly visible structural abnormality. Conversely, an MRI can show abnormalities in people who do not have pain. Diagnosis therefore involves considering symptoms, clinical examination and investigations together.

When should lower back pain be investigated?

Further investigation may be appropriate when symptoms are persistent or worsening, neurological symptoms are present, a specific underlying condition is suspected, or an investigation is likely to influence treatment. The appropriate approach depends upon the individual clinical circumstances.

About This Article

This article provides general information about possible causes of lower back pain. It is not intended to diagnose the cause of an individual's symptoms or replace personalised medical advice.

Medically reviewed by Professor Nasir A. Quraishi
Consultant Spinal Surgeon & Honorary Professor

Clinical sources: NICE guidance on low back pain and sciatica in people aged 16 and over, and NHS guidance on back pain and sciatica.

Further Information About Lower Back Pain

If you are experiencing persistent or significant lower back pain, an assessment can help establish whether further investigation or specialist treatment may be appropriate.

Learn more about Lumbar / Back Pain

When Should I See a Spine Specialist for Back Pain?
MRI Scans for Lower Back Pain: When Are They Needed?
Slipped Disc: Symptoms, Diagnosis and Treatment
Lumbar Spinal Stenosis: Symptoms and Treatment