Low back pain: causes, treatment and red flags

If you’ve spent days with a nagging ache in your lower back that just won’t settle, you’re probably looking for concrete answers: why is this happening, how long will it last and what should you actually do about it. Low back pain is one of the most frequent reasons for medical consultation in the world, and it is also one of the most surrounded by myths. This guide helps you understand what is happening, what real options you have and when it’s worth asking a specialist for help.

What is low back pain?

Low back pain is any pain, stiffness or tension in the lower region of the back, between the last ribs and the buttock creases. It is so common that 60% to 80% of people experience it at least once in their lifetime (Hartvigsen et al., Lancet 2018).

The lumbar region is made up of five large vertebrae (L1 to L5), separated by intervertebral discs that absorb load and allow movement. Around them sit deep muscles (multifidus, transversus abdominis), ligaments, facet joints and nerve roots branching out toward the legs. Any of these structures can generate pain, and quite often pain comes from several of them at the same time.

Classifying the pain helps you understand it:

• Acute low back pain: lasts less than 4 weeks. This is by far the most common presentation.
• Sub-acute low back pain: 4 to 12 weeks. Worth looking more carefully at what’s perpetuating the problem.
• Chronic low back pain: more than 12 weeks. Usually involves multiple factors, not just anatomical ones.

International clinical guidelines draw another important distinction:

• Non-specific low back pain: around 85-90% of cases. No clear structural lesion and no single identifiable cause.
• Low back pain with radicular involvement: 5-10% of cases. A nerve root is involved (sciatica, cruralgia).
• Low back pain with a specific serious cause: less than 1%. Includes fractures, infections, tumors or cauda equina syndrome.

Knowing which category you are in completely changes the strategy.

Symptoms

Main symptoms

• A dull or tight pain in the lumbar region, sometimes with a “heavy” feeling.
• Morning stiffness or stiffness after staying in the same position for a while.
• Pain that increases when you bend forward, lift something heavy, cough or sneeze.
• Visible or palpable muscle tightness alongside the spine.

Symptom patterns

Depending on which structure is irritated, the pain behaves differently:

• Pure mechanical pain: worse with movement and better with rest. Usually comes from muscles, ligaments or facet joints.
• Pain radiating to the leg (sciatica or cruralgia): suggests nerve root involvement, usually from a lumbar herniated disc or spinal canal stenosis.
• Pain that changes with posture: if it gets worse when you walk and improves when you lean forward or sit down, it may point to lumbar spinal stenosis.
• Night-time pain that wakes you up: always warrants medical evaluation. It is not typical of mechanical pain.

Red flags

Seek emergency care if any of the following appear:

• Loss of bladder or bowel control.
• Numbness in the genital or “saddle” area (between the legs).
• Rapidly progressive weakness in one or both legs.
• High fever alongside intense low back pain.
• Significant recent trauma (fall from height, traffic accident).
• History of cancer with new pain that does not settle.
• Unexplained weight loss together with the pain.

These signs can indicate cauda equina syndrome, a spinal infection, a fracture or a tumour. They are uncommon, but timely diagnosis matters.

Causes

Low back pain rarely has a single cause. Most often it is a combination of mechanical, degenerative and contextual factors.

Mechanical causes

• Muscle overload: heavy lifting with poor technique, unusual effort, long hours in poor posture.
• Ligament or fascia injury: from sudden movements or loaded rotations.
• Facet joint dysfunction: the small joints between vertebrae get irritated from overuse or osteoarthritis.

Degenerative causes

• Degenerative disc disease: intervertebral discs lose water over the years, become less elastic and cushion less well.
• Herniated disc: the disc’s nucleus shifts and can compress a nerve root. More common in people aged 30 to 50.
• Lumbar spinal stenosis: narrowing of the space through which nerves pass, typically in people over 60.
• Spondylolisthesis: one vertebra slips relative to the next.

Inflammatory or specific causes

Less frequent but important to rule out:

• Axial spondyloarthritis (inflammatory arthritis of the spine).
• Spinal or disc infections.
• Fractures from osteoporosis, especially in postmenopausal women.
• Primary or metastatic tumors (very rare).

Factors that amplify pain without directly causing it

These don’t “cause” the pain but do prolong episodes and make them more intense:

• Sustained stress and sleep disorders.
• Anxiety and depressive conditions.
• Fear of movement (kinesiophobia).
• Catastrophic expectations (“this is going to cripple me”).

Current evidence recognizes that chronic low back pain is a biopsychosocial phenomenon, not a purely anatomical one (Foster et al., Lancet 2018).

Risk factors

Some factors increase the likelihood of having an episode of low back pain or of it becoming chronic:

• Age between 30 and 60 (peak incidence).
• Sedentary lifestyle or, at the other extreme, intense physical load without proper progression.
• Sustained poor posture habits (hours at a screen, driving, lifting).
• Overweight or obesity, due to chronic overload.
• Smoking, which reduces blood flow to the intervertebral disc.
• Previous episodes of low back pain (the best predictor of a new episode is having had one).
• Untreated mood or sleep disorders.
• Job dissatisfaction or physically demanding work without support.

Complications

Most episodes of low back pain resolve without lasting damage. When poorly managed, however, it can lead to:

• Chronicity: moving from acute to chronic. This is the most common complication and the most costly, both personally and economically.
• Functional disability: persistent limitation for working, doing sport or daily activities.
• Neurological deficit: persistent loss of strength or sensation if radicular involvement is left untreated.
• Prolonged analgesic use: with risk of gastrointestinal, renal and — in the case of opioids — dependence-related adverse effects.
• Physical deconditioning: muscles that atrophy from avoiding movement, perpetuating the cycle.

Understanding this early changes the outlook.

How low back pain is diagnosed

The diagnosis of low back pain does not, in most cases, rely on sophisticated imaging. It rests on three pillars.

1. Clinical history

The specialist will ask you structured questions:

• When did it start? Was there a clear trigger?
• What makes it better and what makes it worse?
• Does it hurt more when you move or when you rest?
• Does it radiate into the leg? How far?
• Is there tingling, numbness or weakness?
• How are you sleeping? How is your mood?
• Have you had episodes before? How did they resolve?

This conversation guides a large portion of the diagnosis. Clinical guidelines agree that history-taking comes first and is the most important step (NICE NG59, 2016 (upd. 2020)).

2. Physical examination

Includes observation of posture and gait, palpation of the area, lumbar range of motion, specific maneuvers (Lasègue, Bragard, Slump test), and assessment of reflexes, strength and sensation in the legs. The goal is to identify whether there is nerve root involvement and which structures may be generating the pain.

3. Imaging (when appropriate)

Here lies one of the most widespread myths: the belief that MRI is the first step. It is not in most cases.

• Plain X-ray: useful when fracture, alignment issues or scoliosis follow-up are suspected.
• Magnetic resonance imaging (MRI): indicated when there is persistent radicular involvement, suspicion of a serious specific cause, or when conservative treatment fails after 6 weeks.
• CT scan: useful for bony structures and when MRI is not possible.
• Electromyography: assesses the degree of nerve conduction impairment when weakness is present.

A relevant fact that changes the conversation with the patient: in pain-free people, MRI shows disc degeneration in 37% of 20-year-olds and more than 90% of 60-year-olds (Brinjikji et al., AJNR 2015). Seeing “a herniated disc” on the report does not mean that is the source of pain.

That is why international guidelines recommend not ordering imaging in the first 4-6 weeks if there are no red flags.

Treatment

The current approach, backed by major clinical guidelines (ACP 2017, NICE NG59 2016 (upd. 2020)), prioritizes non-invasive treatments in most cases.

Conservative treatment (first line)

Patient education. Understanding what is happening reduces fear of movement and improves outcomes. It is not an extra; it is an intervention with evidence behind it.

Stay as active as tolerated. Prolonged bed rest has been shown to worsen outcomes. Walking, moving and gradually returning to normal activities is part of the treatment, not something to do “once it has passed”.

Physical therapy and therapeutic exercise. The intervention with the most evidence for sub-acute and chronic pain. Includes core stabilization, mobility work, motor control and, when appropriate, progressive strengthening.

Cognitive functional therapy (CFT). A relatively new approach backed by a phase 3 clinical trial with 3-year follow-up (Kent et al., The Lancet, 2023; Hancock et al., The Lancet Rheumatology, 2025). It combines pain education, graded exposure to movement, and work on the beliefs and emotions that keep pain going over time. CFT produced large and sustained improvements in disability and pain in people with chronic low back pain compared with usual care — and the effect held at 3 years. It is the intervention that best reflects the biopsychosocial model of chronic pain.

Pain management. The preferred starting point is acetaminophen (paracetamol) and oral anti-inflammatories, always considering each patient’s risk profile (gastrointestinal, cardiovascular, renal). Muscle relaxants can be used for short periods. Opioids are reserved for very specific, supervised cases.

Complementary therapies. Spinal manipulation, acupuncture, yoga or mindfulness may help selected patients, particularly in chronic pain, per the ACP.

Image-guided injections. Useful in specific cases with persistent radicular involvement, under specialist judgment.

Surgery (when it is considered)

Surgery is a tool, not the first choice. It is considered when:

• There is progressive neurological deficit (for example, foot weakness that worsens week by week).
• There is cauda equina syndrome (surgical emergency).
• Disabling radicular pain does not respond to 6-12 weeks of properly managed conservative treatment.
• There is a clear structural cause (large symptomatic herniated disc, severe stenosis with neurogenic claudication, unstable spondylolisthesis, fracture).

The decision to operate is made together. It factors in the MRI, the physical examination, the progress with conservative treatment and your preferences. An MRI showing a herniation is not, by itself, an indication for surgery.

If your case has a specific structural cause such as a herniated disc that meets surgical criteria, it may be covered by Chile’s GES/AUGE system, with statutory deadlines for surgery and follow-up. The process to activate GES coverage for lumbar herniated disc details the formal steps and the binding clinical criteria.

Prevention

No one is immune to an episode of low back pain, but there are measures that clearly reduce the likelihood and severity:

• Regular physical activity. Aerobic and strength exercise, at least 150 minutes per week, is the preventive intervention with the best evidence. A 2024 randomised trial (WalkBack, Lancet) showed that a simple program of progressive walking plus education roughly halves the chance of low back pain recurrence at 12 months compared with usual care (Pocovi et al., The Lancet, 2024).
• Core strengthening. Deep trunk musculature (multifidus, transversus, diaphragm, pelvic floor) stabilises the spine and reduces recurrences.
• Lifting technique. Bend the knees, keep the load close to the body, avoid rotation under load.
• Reasonable ergonomics. A chair that supports the lumbar curve, screen at eye level, active breaks every 45-60 minutes.
• Healthy body weight.
• Quit smoking. It affects disc health.
• Sleep hygiene. 7-9 hours on a medium-firm mattress, sleeping on your side with a pillow between the knees or on your back with a pillow under the knees.
• Stress management. This is not “just psychological”; sustained stress amplifies pain through real neurophysiological pathways.

When to see an orthopedic spine specialist

Not every episode of low back pain needs a specialist from day one. But there are scenarios where it no longer makes sense to wait:

• Pain persists more than 6 weeks despite reasonable conservative treatment.
• Pain radiates to the leg with tingling, numbness or weakness.
• You’ve had several episodes in the past year, each triggered more easily than the last.
• Pain interferes with your sleep, work or daily life.
• You’ve had an MRI and you don’t fully understand what the findings mean.
• Surgery has already been recommended and you want a second opinion before deciding.

An orthopedic spine specialist can put all the information together, rule out serious causes, confirm whether there is significant radicular involvement and design a structured recovery plan tailored to your case.

Myths and realities

Conclusion

Low back pain is common, almost always benign at onset, and in most cases improves with well-delivered conservative management: understanding what is happening, staying active within your limits, guided therapeutic exercise and time. Early specialist assessment makes sense when there are red flags, persistent radiating pain, repeated recurrences or when you need clarity about an MRI report.

Persistent low back pain, the presence of red flags, or an imaging report that doesn’t match your symptoms are reasonable grounds for specialized evaluation. If you want to review your case with clinical judgment — to rule out what matters, decide whether you need additional studies, and build a concrete plan — you can schedule a teleconsult with Dr. Yoshiro Sato. The consultation is via video call, lasts 30 minutes, and includes review of your imaging.

This content is for educational purposes and does not replace evaluation by an orthopedic spine specialist. If you have persistent symptoms or red flags, consult a physician.

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