Causes of Low Back Pain

 

What causes lower back pain?

 

As you age, your bone strength and muscle elasticity and tone tend to decrease. The discs begin to lose fluid and flexibility, which decreases their ability to cushion the vertebrae.

 

Back pain can occur anywhere in the back most common is the lower back when for example, you lift objects too heavy or overstretches, causing a sprain, strain, or spasm in one of the muscles or ligaments in the back.

 

If the spine becomes overly strained or compressed, a disc may rupture or bulge outward. This rupture may put pressure on one of the more than 50 nerves rooted to the spinal cord that control body movements and transmit signals from the body to the brain. When these nerve roots become compressed or irritated, this results to back pain.

 

Low back pain may come from a nerve or muscle irritation or bone lesions. Most low back pain follows injury or trauma to the back, but pain may also be caused by degenerative conditions such as arthritis or disc disease, osteoporosis or other bone diseases, viral infections, irritation to joints and discs, or congenital abnormalities in the spine. Obesity, smoking, weight gain during pregnancy, stress, poor physical condition, posture inappropriate for the activity being performed, and poor sleeping position also may contribute to low back pain.

 

Additionally, scar tissue created when the injured back heals itself does not have the strength or flexibility of normal tissue. Buildup of scar tissue from repeated injuries eventually weakens the back and can lead to more serious injury.

 

Occasionally, low back pain may indicate a more serious medical problem. Pain accompanied by fever or loss of bowel or bladder control, pain when coughing, and progressive weakness in the legs may indicate a pinched nerve or other serious condition. People with diabetes may have severe back pain or pain radiating down the leg related to neuropathy. People with these symptoms should contact a doctor immediately to help prevent permanent damage.

 

Common Causes of Low Back Pain

Most low back pain is triggered by some combination of overuse, muscle strain, and injury to the muscles, ligaments, and discs that support the spine. Many experts believe that over time muscle strain can lead to an overall imbalance in the spinal structure. This leads to a constant tension on the muscles, ligaments, bones, and discs, making the back more prone to injury or re-injury.

The causes of pain in the low back, or lumbosacral region, tend to add on to one another. For example, after straining muscles, you are likely to walk or move in different ways to avoid pain or to use muscles that aren't sore. That can cause you to strain other muscles that don't usually move that way.

 

The most common causes of low back pain are:

• Injury or overuse of muscles, ligaments, facet joints, and the sacroiliac joints.
• Pressure on nerve roots in the spinal canal. Nerve root compression can be caused by:
o A herniated disc, often brought on by repeated vibration or motion (as during machine use or sport activity, or when lifting improperly), or by a sudden heavy strain or increased pressure to the lower back.
o Osteoarthritis (joint degeneration), which typically develops with age. When osteoarthritis affects the small facet joints in the spine, it can lead to back pain. Osteoarthritis in other joints, such as the hips, can cause you to limp or to change the way you walk. This can also lead to back pain.
o Spondylolysis and spondylolisthesis, vertebra defects that can allow a vertebra to slide over another when aggravated by certain activities.
o Spinal stenosis, or narrowing of the spinal canal, which typically develops with age.
o Fractures of the vertebrae caused by significant force, such as from an auto or bicycle accident, a direct blow to the spine, or compressing the spine by falling onto the buttocks or head.
o Spinal deformities, including curvature problems such as severe scoliosis or kyphosis.
o Synovial Cyst in the Lumbar Spine
• Compression fractures. Compression fractures are more common among postmenopausal women with osteoporosis, or in men or women after long-term corticosteroid use. In a person with osteoporosis, even a small amount of force put on the spine, as from a sneeze, may cause a compression fracture.
o Vertebral Compression Fractures and Back Pain- Since they are major load bearing structures, vertebral bodies are also prone to developing compression fractures, particularly in patients with osteoporosis (which weakens the bone). These fractures can lead to chronic back pain and progressive misalignment or deformity of the spine.

Over time, a misalignment or deformity in the spine places stress on muscles, tendons, ligaments, and bones throughout the back and can result in impaired balance or walking ability.

Common causes of low back pain (lumbar backache) include lumbar strain, nerve irritation, lumbar radiculopathy, bony encroachment, and conditions of the bone and joints.

1. Lumbar strain (acute, chronic)

A lumbar strain is a stretch injury to the ligaments, tendons, and/or muscles of the low back. The stretching incident results in microscopic tears of varying degrees in these tissues. Lumbar strain is considered one of the most common causes of low back pain. The injury can occur because of overuse, improper use, or trauma. Soft-tissue injury is commonly classified as "acute" if it has been present for days to weeks. If the strain lasts longer than three months, it is referred to as "chronic."

Lumbar strain most often occurs in people in their 40s, but it can happen at any age. The condition is characterized by localized discomfort in the low back area with onset after an event that mechanically stressed the lumbar tissues. The severity of the injury ranges from mild to severe, depending on the degree of strain and resulting spasm of the muscles of the low back.

The diagnosis of lumbar strain is based on the history of injury, the location of the pain, and exclusion of nervous system injury. Usually, X-ray testing is only helpful to exclude bone abnormalities.

The treatment of lumbar strain consists of resting the back (to avoid reinjury), medications to relieve pain and muscle spasm, local heat applications, massage, and eventual (after the acute episode resolves) reconditioning exercises to strengthen the low back and abdominal muscles. Initial treatment at home might include heat application, acetaminophen (Tylenol) or ibuprofen (Advil, Motrin), and avoiding reinjury and heavy lifting. Long periods of inactivity in bed are no longer recommended, as this treatment may actually slow recovery. Spinal manipulation for periods of up to one month has been found to be helpful in some patients who do not have signs of nerve irritation. Future injury is avoided by using back-protection techniques during activities and support devices as needed at home or work.

2. Nerve irritation

The nerves of the lumbar spine can be irritated by mechanical pressure (impingement) by bone or other tissues, or from disease, anywhere along their paths -- from their roots at the spinal cord to the skin surface. These conditions include lumbar disc disease (radiculopathy), bony encroachment, and inflammation of the nerves caused by a viral infection (shingles). See discussions of these conditions below.

The nerve passing to the next level runs over a weak spot in the disc space, which is the reason discs tend to herniate (extrude) right under the nerve root and can cause leg pain (lumbar radiculopathy or sciatica).

• Cervical disc herniations (in the neck) tend to irritate the nerve exiting at a particular level (e.g. C6 at C5-C6).
• Lumbar disc herniations (in the low back) tend to irritate the nerve that lies across a particular level (e.g. L5 at L4-L5) .
• Thoracic disc herniations (in the upper back) are very rare.
Sometimes, a herniated disc will cause only leg pain or arm pain and not lower back pain or neck pain, and may initially be thought to be a problem with the patient’s leg or arm.
• Arm pain from a cervical disc herniation is usually accompanied by numbness/tingling and runs to the fingers.
• Leg pain from a lumbar disc herniation will usually run below the knee, and possibly to the foot, and may be accompanied by numbness. Learn more about how a herniated disc in the lower back can affect the sciatic nerve and lead to leg pain and even foot pain.
Pinched Nerve Pathology
The two nerves most commonly pinched in the lower back are L5 (lumbar 5) and S1 (sacral 1).
• Pinched nerve at L5. The L5 nerve supplies the nerves to the muscles that raise the foot and big toe, and consequently, impingement of this nerve may lead to weakness in these muscles. Numbness for L5 runs over the top of the foot.
• Pinched nerve at S1. Impingement of the S1 nerve can lead to weakness with the large gastronemius muscle in the back of the calf, causing difficulty with foot push off. Numbness for the S1 nerve runs on the outside of the foot. The S1 nerve root also supplies innervation for the ankle jerk (tap on the achilles tendon and the foot goes down), and a loss of this reflex indicates S1 impingement, although it does not create loss of function.
Most cervical pathology will lead to pinching of either C6 or C7 nerve roots in the neck, although sometimes the C5 or C8 nerves may be pinched.
Depending on which nerve root is pinched, the following symptoms are likely:
• Pinched nerve at C5. This can cause shoulder pain, deltoid weakness, and possibly a small area of numbness in the shoulder. On physical exam, a patient’s biceps reflex may be diminished.
• Pinched nerve at C6. This can cause weakness in the biceps and wrist extensors, and pain/numbness that runs down the arm to the thumb. On physical exam, the brachioradialis reflex (mid-forearm) may be diminished.
• Pinched nerve at C7. This can cause pain/numbness that runs down the arm to the middle finger. On physical exam, the triceps reflex may be diminished.
• Pinched nerve at C8. This can cause hand dysfunction (this nerve supplies innervation to the small muscles of the hand). Pain/numbness can run to the outside of the hand (little finger) and impair its reflex.

Healing from a Pinched Nerve

The nerve consists of one long cell from the low back or neck down to the foot or hand, so the nerves tend to heal slowly. The nerves heal from the top down, and depending on how much damage is done at the time the nerve becomes impinged (pinched), it may take weeks to months for the nerve to fully to heal.

Treatment of neural impingement is directed at relieving the pain and then allowing the nerve to heal on its own. Nerves need both inflammation and pressure to be painful, so either relieving the inflammation or the pressure can relieve the pain.

3. Lumbar radiculopathy

Lumbar radiculopathy is nerve irritation that is caused by damage to the discs between the vertebrae. Damage to the disc occurs because of degeneration ("wear and tear") of the outer ring of the disc, traumatic injury, or both. As a result, the central softer portion of the disc can rupture (herniate) through the outer ring of the disc and abut the spinal cord or its nerves as they exit the bony spinal column. This rupture is what causes the commonly recognized "sciatica" pain of a herniated disc that shoots from the low back and buttock down the leg. Sciatica can be preceded by a history of localized low-back aching or it can follow a "popping" sensation and be accompanied by numbness and tingling. The pain commonly increases with movements at the waist and can increase with coughing or sneezing. In more severe instances, sciatica can be accompanied by incontinence of the bladder and/or bowels. The sciatica of lumbar radiculopathy typically affects only one side of the body, such as the left side or right side, and not both.

Lumbar radiculopathy is suspected based on the above symptoms. Increased radiating pain when the lower extremity is lifted supports the diagnosis. Nerve testing (EMG/electromyogram and NCV/nerve conduction velocity) of the lower extremities can be used to detect nerve irritation. The actual disc herniation can be detected with imaging tests, such as CAT or MRI scanning.

Treatment of lumbar radiculopathy ranges from medical management to surgery. Medical management includes patient education, medications to relieve pain and muscle spasms, cortisone injection around the spinal cord (epidural injection), physical therapy (heat, massage by a therapist, ultrasound, electrical stimulation), and rest (not strict bed rest but avoiding reinjury). With unrelenting pain, severe impairment of function, or incontinence (which can indicate spinal cord irritation), surgery may be necessary. The operation performed depends on the overall status of the spine and the age and health of the patient. Procedures include removal of the herniated disc with laminotomy (a small hole in the bone of the lumbar spine surrounding the spinal cord), laminectomy (removal of the bony wall), by needle technique (percutaneous discectomy), disc-dissolving procedures (chemonucleolysis), and others.

4. Bony encroachment

Any condition that results in movement or growth of the vertebrae of the lumbar spine can limit the space (encroachment) for the adjacent spinal cord and nerves. Causes of bony encroachment of the spinal nerves include foraminal narrowing (narrowing of the portal through which the spinal nerve passes from the spinal column, out of the spinal canal to the body, commonly as a result of arthritis), spondylolisthesis (slippage of one vertebra relative to another), and spinal stenosis (compression of the nerve roots or spinal cord by bony spurs or other soft tissues in the spinal canal). Spinal-nerve compression in these conditions can lead to sciatica pain that radiates down the lower extremities. Spinal stenosis can cause lower-extremity pains that worsen with walking and are relieved by resting (mimicking the pains of poor circulation). Treatment of these afflictions varies, depending on their severity, and ranges from rest to surgical decompression by removing the bone that is compressing the nervous tissue.

5. Bone and joint conditions

Bone and joint conditions that lead to low back pain include those existing from birth (congenital), those that result from wear and tear (degenerative) or injury, and those that are due to inflammation of the joints (arthritis).

a. Congenital bone conditions -- Congenital causes (existing from birth) of low back pain include scoliosis and spina bifida. Scoliosis is a sideways (lateral) curvature of the spine that can be caused when one lower extremity is shorter than the other (functional scoliosis) or because of an abnormal architecture of the spine (structural scoliosis). Children who are significantly affected by structural scoliosis may require treatment with bracing and/or surgery to the spine. Adults infrequently are treated surgically but often benefit by support bracing.

Spina bifida is a birth defect in the bony vertebral arch over the spinal canal, often with absence of the spinous process. This birth defect most commonly affects the lowest lumbar vertebra and the top of the sacrum. Occasionally, there are abnormal tufts of hair on the skin of the involved area. Spina bifida can be a minor bony abnormality without symptoms. However, the condition can also be accompanied by serious nervous abnormalities of the lower extremities.

b. Degenerative bone and joint conditions -- As we age, the water and protein content of the body's cartilage changes. This change results in weaker, thinner, and more fragile cartilage. Because both the discs and the joints that stack the vertebrae (facet joints) are partly composed of cartilage, these areas are subject to wear and tear over time (degenerative changes). Degeneration of the disc is called spondylosis. Spondylosis can be noted on X-rays of the spine as a narrowing of the normal "disc space" between the vertebrae. It is the deterioration of the disc tissue that predisposes the disc to herniation and localized lumbar pain ("lumbago") in older patients. Degenerative arthritis (osteoarthritis) of the facet joints is also a cause of localized lumbar pain that can be detected with plain X-ray testing. These causes of degenerative back pain are usually treated conservatively with intermittent heat, rest, rehabilitative exercises, and medications to relieve pain, muscle spasm, and inflammation.

c. Injury to the bones and joints -- Fractures (breakage of bone) of the lumbar spine and sacrum bone most commonly affect elderly people with osteoporosis, especially those who have taken long-term cortisone medication. For these individuals, occasionally even minimal stresses on the spine (such as bending to tie shoes) can lead to bone fracture. In this setting, the vertebra can collapse (vertebral compression fracture). The fracture causes an immediate onset of severe localized pain that can radiate around the waist in a band-like fashion and is made intensely worse with body motions. This pain generally does not radiate down the lower extremities. Vertebral fractures in younger patients occur only after severe trauma, such as from motor-vehicle accidents or a convulsive seizure.

In both younger and older patients, vertebral fractures take weeks to heal with rest and pain relievers. Compression fractures of vertebrae associated with osteoporosis can also be treated with a procedure called vertebroplasty, which can help to reduce pain. In this procedure, a balloon is inflated in the compressed vertebra, often returning some of its lost height. Subsequently, a "cement" (methymethacrylate) is injected into the balloon and remains to retain the structure and height of the body of the vertebra.

d. Arthritis -- The spondyloarthropathies are inflammatory types of arthritis that can affect the lower back and sacroiliac joints. Examples of spondyloarthropathies include reactive arthritis (Reiter's disease), ankylosing spondylitis, psoriatic arthritis, and the arthritis of inflammatory bowel disease. Each of these diseases can lead to low back pain and stiffness, which is typically worse in the morning. These conditions usually begin in the second and third decades of life. They are treated with medications directed toward decreasing the inflammation. Newer biologic medications have been greatly successful in both quieting the disease and stopping its progression.


Less Common Causes of Lower Back Pain

Less common spinal conditions that can cause low back pain include:

• Ankylosing spondylitis, which is a form of joint inflammation (arthritis) that most often affects the spine.

• Bacterial infection. Bacteria are usually carried to the spine through the bloodstream from an infection somewhere else in the body or from IV drug use. But bacteria can enter the spine directly during surgery or injection treatments, or as the result of injury. Back pain may be the result of an infection in the bone (osteomyelitis), in the spinal discs, or in the spinal cord.

• Spinal tumors, or growths that develop on the bones and ligaments of the spine, on the spinal cord, or on nerve roots.

• Paget's disease, which causes abnormal bone growth most often affecting the pelvis, spine, skull, chest, and legs.

• Scheuermann's disease, in which one or more of the bones of the spine (vertebrae) develop wedge-shaped deformities. This causes curvature of the spine (rounding of the back, or kyphosis), most commonly in the chest region.

• Failed back surgery syndrome, which means that a person is still having significant symptoms after surgery.

• Other causes of low back pain include kidney problems, pregnancy, ovary problems, and tumors.

Kidney problems

Kidney infections, stones, and traumatic bleeding of the kidney (hematoma) are frequently associated with low back pain. Diagnosis can involve urine analysis, sound-wave tests (ultrasound), or other imaging studies of the abdomen.

Pregnancy

Pregnancy commonly leads to low back pain by mechanically stressing the lumbar spine (changing the normal lumbar curvature) and by the positioning of the baby inside of the abdomen. Additionally, the effects of the female hormone estrogen and the ligament-loosening hormone relaxin may contribute to loosening of the ligaments and structures of the back. Pelvic-tilt exercises and stretches are often recommended for relieving this pain. Women are also recommended to maintain physical conditioning during pregnancy according to their doctors' advice.

Ovary problems

Ovarian cysts, uterine fibroids, and endometriosis not infrequently cause low back pain. Precise diagnosis can require gynecologic examination and testing.

Tumors

Low back pain can be caused by tumors, either benign or malignant, that originate in the bone of the spine or pelvis and spinal cord (primary tumors) and those which originate elsewhere and spread to these areas (metastatic tumors). Symptoms range from localized pain to radiating severe pain and loss of nerve and muscle function (even incontinence of urine and stool) depending on whether or not the tumors affect the nervous tissue. Tumors of these areas are detected using imaging tests, such as plain X-rays, nuclear bone scanning, and CAT and MRI scanning.

Uncommon causes of low back pain include Paget's disease of bone, bleeding or infection in the pelvis, infection of the cartilage and/or bone of the spine, aneurysm of the aorta, and shingles.

Paget's disease of bone

Paget's disease of the bone is a condition of unknown cause in which the bone formation is out of synchrony with normal bone remodeling. This condition results in abnormally weakened bone and deformity and can cause localized bone pain, though it often causes no symptoms. Paget's disease is more common in people over the age of 50. Heredity (genetic background) and certain unusual virus infections have been suggested as causes. Thickening of involved bony areas of the lumbar spine can cause the radiating lower extremity pain of sciatica.

Paget's disease can be diagnosed on plain X-rays. However, a bone biopsy is occasionally necessary to ensure the accuracy of the diagnosis. Bone scanning is helpful to determine the extent of the disease, which can involve more than one bone area. A blood test, alkaline phosphatase, is useful for diagnosis and monitoring response to therapy. Treatment options include aspirin, other anti-inflammatory medicines, pain medications, and medications that slow the rate of bone turnover, such as calcitonin (Calcimar, Miacalcin), etidronate (Didronel), alendronate (Fosamax), risedronate (Actonel), and pamidronate (Aredia).

Bleeding or infection in the pelvis

Bleeding in the pelvis is rare without significant trauma and is usually seen in patients who are taking blood-thinning medications, such as warfarin (Coumadin). In these patients, a rapid-onset sciatica pain can be a sign of bleeding in the back of the pelvis and abdomen that is compressing the spinal nerves as they exit to the lower extremities. Infection of the pelvis is infrequent but can be a complication of conditions such as diverticulosis, Crohn's disease, ulcerative colitis, pelvic inflammatory disease with infection of the Fallopian tubes or uterus, and even appendicitis. Pelvic infection is a serious complication of these conditions and is often associated with fever, lowering of blood pressure, and a life-threatening state.

Infection of the cartilage and/or bone of the spine

Infection of the discs (septic discitis) and bone (osteomyelitis) is extremely rare. These conditions lead to localized pain associated with fever. The bacteria found when these tissues are tested with laboratory cultures include Staphylococcus aureus and Mycobacterium tuberculosis (TB bacteria). TB infection in the spine is called Pott's disease. These are each very serious conditions requiring long courses of antibiotics. The sacroiliac joints rarely become infected with bacteria. Brucellosis is a bacterial infection that can involve the sacroiliac joints and is usually transmitted in goat's milk.

Aneurysm of the aorta

In the elderly, atherosclerosis can cause weakening of the wall of the large arterial blood vessel (aorta) in the abdomen. This weakening can lead to a bulging (aneurysm) of the aorta wall. While most aneurysms cause no symptoms, some cause a pulsating low back pain. Aneurysms of certain size, especially when enlarging over time, can require surgical repair with a grafting procedure to repair the abnormal portion of the artery.

Shingles

Shingles (herpes zoster) is an acute infection of the nerves that supply sensation to the skin, generally at one or several spinal levels and on one side of the body (right or left). Patients with shingles usually have had chickenpox earlier in life. The herpes virus that causes chickenpox is believed to exist in a dormant state within the spinal nerve roots long after the chickenpox resolves. In people with shingles, this virus reactivates to cause infection along the sensory nerve, leading to nerve pain and usually an outbreak of shingles (tiny blisters on the same side of the body and at the same nerve level). The back pain in patients with shingles of the lumbar area can precede the skin rash by days. Successive crops of tiny blisters can appear for several days and clear with crusty inflammation in one to two weeks. Patients occasionally are left with a more chronic nerve pain (postherpetic neuralgia). Treatment can involve symptomatic relief with lotions, such as calamine, or medications, such as acyclovir (Zovirax) for the infection and pregabalin (Lyrica) or lidocaine (Lidoderm) patches for the pain.