Low Back Pain

The lumbar spine, or 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, this complex structure also leaves the low back susceptible to injury and pain.

The lumbar spine, what can go wrong

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. Nerves in the low back supply sensation and power the muscles in the pelvis, legs, and feet.

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

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. For example, a degenerated or torn lumbar 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 torn disc may or may not. The time course of pain helps determine the cause.

Range of lower back pain symptoms

Low back pain can incorporate a wide variety of symptoms. It can be mild and merely annoying, or it can be severe and debilitating. Low back pain may start suddenly, or it could start slowly – possibly coming and going – and gradually get worse over time.

Depending on the underlying cause of the pain, symptoms can be experienced in a variety of ways. For example:

• Pain that is dull or achy, contained to the low back
• Stinging, burning pain that moves from the low back to the backs of the thighs, sometimes into the lower legs or feet; can include numbness or tingling (sciatica)
• Muscle spasms and tightness in the low back, pelvis, and hips
• Pain that worsens after prolonged sitting or standing
• Difficulty standing up straight, walking, or going from standing to sitting

In addition, symptoms of lower back pain are usually described by type of onset and duration:

• Acute pain. This type of 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, this type of pain is usually mechanical in nature (such as a muscle strain or joint pain) but is prolonged. At this point, a medical workup may be considered, and is advisable if the pain is severe and limits one’s ability to participate in activities of daily living, sleeping, and working.
• Chronic back pain. Usually defined as lower back pain that 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.1

Types of low back pain

There are many ways to categorize low back pain – two common types include:

• Mechanical pain. By far the most common cause of lower 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.
• Radicular pain. This type of pain can occur if a spinal nerve root becomes impinged or inflamed. 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.

There are many additional sources of pain, including claudication pain (from stenosis) myelopathic pain, neuropathic pain, deformity, tumors, infections, pain from inflammatory conditions (such as rheumatoid arthritis or ankylosing spondylitis), and pain that originates from another part of the body and presents in the lower back (such as kidney stones, or ulcerative colitis).

It is also possible for low back pain to develop with no definitive cause. When this happens, the primary focus is on treating the symptoms (rather than the cause of the symptoms) and the patient’s overall health.

For subacute and chronic lower back pain, a thorough diagnosis is important to lay the foundation for appropriate treatment and rehabilitation. Lower back pain treatment reduces the likelihood of recurrent back pain flare-ups and helps prevent the development of chronic lower back pain.

Causes

Causes of lower back pain

Most commonly, mechanical issues and soft-tissue injuries are the cause of low back pain. These injuries can include damage to the intervertebral discs, compression of nerve roots, and improper movement of the spinal joints.

The single most common cause of lower back pain is a torn or pulled muscle and/or ligament.

Muscle strain and ligament sprain

A low back sprain or strain can happen suddenly, or can develop slowly over time from repetitive movements.

• Strains occur when a muscle is stretched too far and tears, damaging the muscle itself.
• Sprains happen when over-stretching and tearing affects ligaments, which connect the bones together.

For practical purposes, it does not matter whether the muscle or ligament is damaged, as the symptoms and treatment are the same.

Common causes of sprain and strain include:

• Lifting a heavy object, or twisting the spine while lifting
• Sudden movements that place too much stress on the low back, such as a fall
• Poor posture over time
• Sports injuries, especially in sports that involve twisting or large forces of impact

While sprains and strains do not sound serious and do not typically cause long-lasting pain, the acute pain can be quite severe.

Causes of chronic lower back pain

Pain is considered chronic once it lasts for more than three months and exceeds the body’s natural healing process. Chronic pain in the low back often involves a disc problem, a joint problem, and/or an irritated nerve root. Common causes include:

Lumbar herniated disc. The jelly-like center of a lumbar disc can break through the tough outer layer and irritate a nearby nerve root. The herniated portion of the disc is full of proteins that cause inflammation when they reach a nerve root, and inflammation, as well as nerve compression, cause nerve root pain. The disc wall is also richly supplied by nerve fibers, and a tear through the wall can cause severe pain.

Degenerative disc disease. At birth, intervertebral discs are full of water and at their healthiest. As people age over time, discs lose hydration and wear down. As the disc loses hydration, it cannot resist forces as well, and transfers force to the disc wall that may develop tears and cause pain or weakening that can lead to a herniation. The disc can also collapse and contribute to stenosis.

Facet joint dysfunction. There are two facet joints behind each disc at each motion segment in the lumbar spine. These joints have cartilage between the bones and are surrounded by a capsular ligament, which is richly innervated by nerves. These joints can be painful by themselves, or in conjunction with disc pain.

Sacroiliac joint dysfunction. The sacroiliac joint connects the sacrum at the bottom of the spine to each side of the pelvis. It is a strong, low-motion joint that primarily absorbs shock and tension between the upper body and the lower body. The sacroiliac joint can become painful if it becomes inflamed (sacroiliitis) or if there is too much or too little motion of the joint.

Spinal stenosis. This condition causes pain through narrowing of the spinal canal where the nerve roots are located. The narrowing can be central, forminal, or both, and can be at a single level or multiple levels in the lower back.

Spondylolisthesis. This condition occurs when one vertebra slips over the adjacent one. There are 5 types of spondylolisthesis but the most common are secondary to a defect or fracture of the pars (between the facet joints) or mechanical instability of the facet joints (degenerative). The pain can be caused by instability (back) or compression of the nerves (leg).

Osteoarthritis. This condition results from wear and tear of the disc and facet joints. It causes pain, inflammation, instability, and stenosis to a variable degree, and can occur at a single level or multiple levels of the lower spine. Spinal osteoarthritis is associated with aging and is slowly progressive. It is also referred to as spondylosis or degenerative joint disease.

Deformity. Curvature of the spine can include scoliosis or kyphosis. The deformity may be associated with lower back pain if it leads to the breakdown of the discs, facet joints, sacroiliac joints or stenosis.

Trauma. Acute fractures or dislocations of the spine can lead to pain. Lower back pain that develops after a trauma, such as a motor vehicle accident or a fall, should be medically evaluated.

Compression fracture. A fracture that occurs in the cylindrical vertebra, in which the bone essentially caves in on itself, can cause sudden pain. This type of fracture is most common due to weak bones, such as from osteoporosis, and is more common in older people.

It is important to note that the presence of one or more of these conditions does not necessarily mean that is the cause of pain. For example, osteoarthritis or degenerative disc disease could appear on an imaging study but the person may not report pain.

Less common causes of low back pain

While considerably less common, low back pain may also be caused by:

Infection. Also called osteomyelitis, a spinal infection is rare but can cause severe pain and is life threatening if untreated. It can be caused by surgical procedures, injections, or spread through the blood stream. Patients with a compromised immune system are more susceptible to developing an infection in the spine.

Tumor. Most spinal tumors start in another part of the body and metastasize to the spine. The most common tumors that spread to the spine start from cancer in the breast, prostate, kidney, thyroid, or lung. Any new symptoms of back pain in a patient with a known diagnosis of cancer should be evaluated for possible spinal metastasis.

Autoimmune disease. Back pain is a possible symptom associated with autoimmune conditions, such as ankylosing spondylitis, rheumatoid arthritis, lupus, crohn’s disease, fibromyalgia, and others.

Symptoms

Lower back pain symptoms

Low back pain might begin as acute due to an injury, but can become chronic. Managing pain appropriately at an early stage can help limit symptoms in both time and severity.

Low back pain is typically characterized by a combination of the following symptoms:

Dull, aching pain

Pain that remains within the low back (axial pain) is usually described as dull and aching rather than burning, stinging, or sharp. This kind of pain can be accompanied by mild or severe muscle spasms, limited mobility, and aches in the hips and pelvis.

Pain that travels to the buttocks, legs, and feet

Sometimes low back pain includes a sharp, stinging, tingling or numb sensation that moves down the thighs and into the low legs and feet, also called sciatica. Sciatica is caused by irritation of the sciatic nerve, and is usually only felt on one side of the body.

Pain that is worse after prolonged sitting

Sitting puts pressure on the discs, causing low back pain to worsen after sitting for long periods of time. Walking and stretching can alleviate low back pain quickly, but returning to a sitting position may cause symptoms to return.

Pain that feels better when changing positions

Depending on the underlying cause of pain, some positions will be more comfortable than others. For example, with spinal stenosis walking normally may be difficult and painful, but leaning forward onto something, such as a shopping cart, may reduce pain. How symptoms change with shifting positions can help identify the source of pain.

Pain that is worse after waking up and better after moving around

Many who experience low back pain report symptoms that are worse first thing in the morning. After getting up and moving around, however, symptoms are relieved. Pain in the morning is due to stiffness caused by long periods of rest, decreased blood flow with sleep, and possibly the quality of mattress and pillows used.

Of course, there are other ways people experience low back pain. Low back pain varies on an individual level, and many factors influence the pain experience, including mental and emotional health, financial stress, or exercise and activity level.

Onset of Low Back Pain Symptoms

Depending on the cause of low back pain, the onset of symptoms can vary widely. Back pain may include:

Pain that develops slowly over time

Symptoms caused by repetitive motions or stress-inducing positions tend to come on slowly and progressively worsen. Pain may develop after certain activities or at the end of a long day, and may feel like a constant ache.

Pain that comes and goes, but worsens over time

Low back pain caused by degenerative disc disease can be felt off and on, but pain flare-ups get progressively more severe over a long period of time.

Immediate pain after an injury

Sudden or jarring movements can damage the spine and its supportive muscles, causing immediate, acute pain.

Delayed symptoms after injury

Sometimes symptoms develop or get worse a few hours or days after an accident or injury. Delayed pain is generally thought of as a side effect of natural healing processes of muscles.

Low back pain symptoms by location

The body’s largest vertebrae are found in the lumbar spine, supporting most of the weight of the upper body. These vertebrae are highly susceptible to degeneration and injury, and an injury at one spinal level can cause a specific set of symptoms:

L3-L4

The L3-L4 nerve root is likely to cause shooting pain in the front of the thigh, possibly including numbness or tingling. Pain or neurological symptoms may radiate to the front of the knee, shin, and foot as well, though it is less common.

L4-L5

Pain from the L4-L5 segment typically manifests as sciatic pain in the back of the thigh, and possibly pain that reaches the calves, combined with axial low back pain.

L5-S1

Where the base of the spine connects to the sacrum there are a couple of joints that provide support and flexibility. One is the lumbosacral joint, which allows the hips to swing side to side, and the other is the sacroiliac joint, which has limited mobility and mainly absorbs shock from the upper body to the low body.

Pain from the L5-S1 segment is generally caused by problems with these joints or from a compressed nerve root. Issues with the L5-S1 segment commonly cause sciatica.

Different nerve roots are irritated depending on the structures in the back that are injured, and being able to point to the specific areas of radicular pain can help more precisely diagnose the source of low back pain.

Symptoms that require immediate attention

Sometimes low back pain can signal a serious underlying medical condition. People who experience any of the following symptoms are advised to seek immediate care.

• Loss of bladder and bowel control
• Recent weight loss not due to lifestyle changes, such as diet and exercise
• Fever and chills
• Severe, unrelenting pain in the abdomen

Additionally, people who experience pain symptoms after a major trauma (such as a car accident) 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.

Chronic low back pain is usually correlated with other symptoms. Most people with ongoing low back pain and/or leg pain report difficulty with sleeping (falling asleep and/or staying asleep), depression and anxiety.