The low back is a remarkably well-engineered structure of interconnecting bones, joints, nerves, ligaments, and muscles, all working together to provide support, strength, and flexibility.

However, any problem that develops in this complex anatomical structure can lead to intense and/or chronic low back pain.

Identifying the underlying cause of one’s pain is important to select a treatment based on today’s best medical practices.

This guide provides in-depth medical information on lower back pain causes and treatments.

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The lumbar region of the spine, commonly known as the lower back, consists of five vertebrae labeled L1 through L5 and is situated between the thoracic, or chest, region of the spine and the sacrum.

The two lowest segments in the lumbar spine, L4-L5 and L5-S1, carry the most weight and experience maximum movement, making these segments prone to injury and pain.

The most common cause of lower back pain is a torn or pulled muscle. Pain from a pulled back muscle, also called a muscle strain, is acute and often remains localized to the lower back area. A muscle strain can be accompanied by muscle spasms, as the body tries to stabilize the injury.

Lower back pain can also occur due to problems affecting the lumbar spinal discs. The discs can herniate or degenerate, and if the disc material irritates a nearby spinal nerve root, it can cause lower back pain or radiating pain in the legs and feet. This type of pain is called radicular pain or sciatica and travels down the leg through the large sciatic nerve. If the disc material compresses a nerve root, symptoms of radiculopathy, such as numbness, tingling, and weakness may occur in the affected leg.

Another type of lower back pain is called vertebrogenic pain, which occurs when the vertebral endplate, situated between the vertebral body and the intervertebral disc, becomes damaged. This pain is felt as a persistent dull ache or burning pain deep in the lower back area. Vertebrogenic pain usually flares up while sitting, standing, and bending the spine forward. In some cases, the pain may spread into the tissues surrounding the spine and the buttocks.

Dysfunction of the sacroiliac joints is another cause of lower back pain. These joints connect the triangular-shaped sacrum to the hip on each side of the spine. The SI joints can become painful due to chronic trauma or an acute injury. SI joint pain is similar to sciatica and is typically felt in the lower back, buttock, and thigh, along with a feeling of weakness and instability during certain movements or activities.

Other causes of lower back pain are degenerative spinal conditions, which occur due to wear and tear or natural aging of the spine. A few of these conditions include lumbar spinal stenosis, lumbar osteoarthritis, and degenerative spondylolisthesis.

Rarely, certain low back conditions, such as a severely herniated disc, can compress the spinal cord or cauda equina, which is a medical emergency. Symptoms include numbness, loss of balance, lower extremity weakness, and loss of bowel and bladder control.

It is important to understand the underlying cause of lower back pain in order to effectively treat the symptoms.

The Lumbar Spine, What Can Go Wrong

Illustration of the normal lumbar spine and a degenerated lumbar spine highlighting bone and disc problems.

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Discs, muscles, nerves, and joints may cause lower back pain.

The low back supports the weight of the upper body and provides mobility for everyday motions such as bending and twisting.

Muscles in the low back are responsible for flexing and rotating the hips while walking, as well as supporting the spinal column.
Nerve roots in the low back supply sensation and power the muscles in the pelvis, legs, and feet.
Spinal motion segments through the lumbar spine provide a combination of flexibility and motion, especially the lower two segments named L4-L5 and L5-S1.

Most acute low back pain results from injury to the muscles, ligaments, joints, nerves, or discs. The body also reacts to injury by mobilizing an inflammatory healing response. While inflammation sounds minor, it can be surprisingly painful.

There is a significant overlap of nerve supply to many of the discs, muscles, ligaments, and other spinal structures, and it can be difficult for the brain to accurately sense which is the cause of the pain.

Watch Lumbar Spine Anatomy Video

For example, a degenerated disc can feel the same as a pulled muscle – both creating inflammation and painful muscle spasm in the same area. Muscles and ligaments heal rapidly, while a degenerative disc disease typically does not. The time course of pain helps determine the cause.

Low back pain symptoms present in very different ways, for example:

Ranges from mild and annoying to severe and debilitating pain.
It may be confined across the low back or spread down into the buttock and leg.
The symptoms may start suddenly or develop slowly—possibly coming and going—and gradually get worse over time.
The low back pain may feel dull or achy, or alternatively, feel stinging and burning

Tracking and identifying specific symptoms helps to obtain an accurate diagnosis and treatment program.

Acute, Subacute, and Chronic Back Pain

Highlighted area showing muscle tightness and pain in the lower back and pelvis.

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Low back pain symptoms can range from a mild ache to sharp, stabbing pain.

Treatment will usually be guided in part by how the pain started and how long it has lasted.

Acute pain - typically comes on suddenly and lasts for a few days or weeks, and is considered a normal response of the body to injury or tissue damage. The pain gradually subsides as the body heals.
Subacute low back pain - lasting between 6 weeks and 3 months, usually mechanical in nature, such as a muscle strain or joint pain. At this point, a medical workup may be considered, and is advisable if the pain is so bad that it limits one’s ability to participate in activities of daily living, sleeping, and working.
Chronic back pain - lasts over 3 months, this type of pain is usually severe, does not respond to initial treatments, and requires a thorough medical workup to determine the exact source of the pain.¹National Institute of Neurological Disorders and Stroke. Pain: Hope Through Research. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Hope-Through-Research/Pain-Hope-Through-Research. June 9, 2017.

See Types of Back Pain: Acute Pain, Chronic Pain, and Neuropathic Pain

Spinal Segments Most Likely to Cause Low Back Pain

The two lowest motion segments carry the most weight while at the same time have the most flexibility. These two segments are highly susceptible to degeneration and injury:

The one above those, labeled the L3-L4 segment is also susceptible to degeneration and injury.

There are joints at the base of the spine that tend to cause low back pain if they become inflamed (sacroiliitis) or if they become unstable or too stiff – called sacroiliac joint dysfunction.

Categories of Lower Back Pain

There are many ways to categorize low back pain, including:

Mechanical pain

An illustration showing facet joint in the lumbar spinal vertebra.

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Facet joint dysfunction is one cause of mechanical back pain.

Mechanical pain (axial pain) is pain primarily from the muscles, ligaments, joints (facet joints, sacroiliac joints), or bones in and around the spine. This type of pain tends to be localized to the lower back, buttocks, and sometimes the top of the legs. It is usually influenced by loading the spine and may feel different based on motion (forward/backward/twisting), activity, standing, sitting, or resting.

Lumbar spine issues that tend to present as mechanical or axial pain include degenerative disc disease, a herniated disc, vertebrogenic pain, sacroiliac joint pain, spinal stenosis, and vertebral fracture.²Chien JJ, Bajwa ZH. What is mechanical back pain and how best to treat it?. Curr Pain Headache Rep. 2008;12(6):406-411. doi:10.1007/s11916-008-0069-3

Radicular pain

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Lumbar radicular pain typically extends into the buttock and/or leg.

This type of pain can occur if a spinal nerve root becomes impinged or inflamed, commonly caused by a lumbar herniated disc, spinal stenosis, or spondylolisthesis.

Radicular pain may follow a nerve root pattern or dermatome down into the buttock and/or leg. Its specific sensation is sharp, electric, burning-type pain and can be associated with numbness or weakness (sciatica). It is typically felt on only one side of the body.

When Low Back Pain Symptoms are Serious

While relatively rare, lower back pain can be a signal of a serious underlying medical condition.

Anyone who experiences any of the following symptoms should seek immediate medical attention.

Incontinence, which includes any loss of bladder and bowel control (inability to hold in or to pass urine or stool)
Recent unexplained weight loss – losing weight without intention, or weight loss not due to changes in diet and exercise
Back pain accompanied by fever and chills
Severe, unrelenting pain in the abdomen
Progressively worsening neurological symptoms

Additionally, people who experience pain symptoms after a trauma (such as a car accident or a high-impact sports injury) are advised to see a doctor.

If low back pain interferes with daily activities, mobility, sleep, or if there are other troubling symptoms, medical attention should be sought.

As a first step, understanding the likely cause of one’s lower back pain aids in finding the right type of health professional for treatment.

1 National Institute of Neurological Disorders and Stroke. Pain: Hope Through Research. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Hope-Through-Research/Pain-Hope-Through-Research. June 9, 2017.
2 Chien JJ, Bajwa ZH. What is mechanical back pain and how best to treat it?. Curr Pain Headache Rep. 2008;12(6):406-411. doi:10.1007/s11916-008-0069-3

Dr. Peloza is a board-certified, fellowship-trained minimally invasive orthopedic spine surgeon at Midwest Orthopedic and Spine Specialists, MO. Dr. Peloza has given several presentations at medical conferences and scientific meetings on topics that include minimally invasive surgery, scoliosis correction, and lumbar fusion.