Back Pain: Causes, Diagnosis & When to Worry

Back pain is one of the most common reasons people seek medical care, and at some point in life the majority of adults will experience it. While an episode of back pain can be distressing, the most important message is reassuring: the great majority of back pain is mechanical, is not due to serious disease, and settles within a few weeks. Understanding what helps recovery — and recognising the small number of warning signs that need urgent attention — allows most people to manage back pain with confidence.

What is back pain?

Back pain describes discomfort arising from the structures of the lower back — the muscles and ligaments, the small facet joints, the intervertebral discs, and the nerves that pass through. It is often grouped as acute (lasting up to a few weeks), sub-acute, or chronic (persisting beyond about three months).

Most back pain is non-specific, meaning it cannot be traced to a single damaged structure and is not linked to serious underlying disease. This is not a failure of diagnosis; rather, it reflects that ordinary mechanical strain is by far the commonest cause.

Which parts of the spine are affected?

Back pain most commonly affects the lumbar spine — the five vertebrae of the lower back that carry much of the body’s weight and allow bending and twisting. The discs cushion each level, the facet joints guide movement, and nerve roots exit to supply the legs. Pain from the lower back may stay localised or, when a nerve is irritated, spread into the buttock or leg.

Causes and risk factors

Common contributors include:

• Muscle or ligament strain from lifting, bending or awkward movements.
• Age-related wear of the discs and joints.
• A slipped (herniated) disc, which may also irritate a nerve.
• Poor posture and prolonged sitting.
• Reduced physical activity and weak supporting muscles.

Risk factors include sedentary habits, being overweight, heavy or repetitive physical work, smoking, and high psychological stress. Less commonly, back pain reflects infection, fracture, inflammatory disease or, rarely, a tumour.

Symptoms and warning signs (red flags)

Typical mechanical back pain causes aching and stiffness, often worse with movement or certain positions and eased by rest or changing position. Muscle spasm is common.

Seek urgent assessment if back pain is accompanied by any of these red flags:

• Numbness around the groin, buttocks or inner thighs.
• Difficulty passing urine, or loss of bladder or bowel control.
• Significant or worsening weakness in one or both legs.
• Fever, chills or night sweats.
• Unexplained weight loss.
• Severe pain after a major injury, or in someone with osteoporosis or cancer.
• Pain that is constant, progressive or much worse at night.

The combination of numbness around the groin, bladder or bowel changes and leg weakness may indicate cauda equina syndrome, a rare emergency. Fever points to possible infection, and a history of cancer or significant injury raises concern about malignancy or fracture. These features need prompt medical attention.

How back pain is diagnosed

For most people, diagnosis rests on the history and a physical examination. The clinician asks about the pattern of pain, any spread into the legs, and red-flag features, then assesses movement, strength, reflexes and sensation.

Imaging is not routinely needed for uncomplicated back pain. X-rays, MRI or CT are reserved for persistent symptoms, suspected nerve involvement, or red-flag features. MRI is most useful when nerve compression, infection or another specific cause is suspected, because age-related changes appear on scans in many people without pain.

Non-surgical treatment

Non-surgical care helps the great majority of people. Key measures include:

• Staying active and avoiding prolonged bed rest.
• Exercise and physiotherapy to restore movement and strengthen supporting muscles.
• Heat or cold for short-term comfort.
• Simple pain relief where appropriate, used for the shortest helpful period.
• Posture and workplace adjustments, with regular movement breaks.
• Addressing stress, sleep and weight, which influence recovery.

Most acute episodes settle steadily with these measures.

When surgery is considered

Surgery is needed for only a small minority of people with back pain. It is generally considered when there is a clear structural cause with nerve compression — for example, persistent leg pain, weakness or numbness from a slipped disc or spinal stenosis that has not responded to non-surgical care — or in urgent situations such as cauda equina syndrome. Surgery is rarely advised for non-specific back pain alone.

When to see a spine specialist

Most back pain can be managed without specialist input. Consider seeing a spine specialist if pain persists despite several weeks of appropriate care, if it spreads down the leg with numbness or weakness, or if it is significantly limiting daily life. Any urgent red-flag features — particularly bladder or bowel changes, groin numbness, leg weakness, fever or unexplained weight loss — need emergency assessment without delay.