What is the anatomy of the low back?
The first step to understanding the various causes of low back pain is learning about the normal design (anatomy) of the tissues of this area. Important structures of the low back that can be related to symptoms there include the bony lumbar spine (vertebrae, singular = vertebra), discs between the vertebrae, ligaments around the spine and discs, spinal cord and nerves, muscles of the low back, internal organs of the pelvis and abdomen, and the skin covering the lumbar area.
The bony lumbar spine is designed so that vertebrae "stacked" together can provide a movable support structure while also protecting the spinal cord from injury. The spinal cord is composed of nervous tissue that extends down the spinal column from the brain. Each vertebra has a spinous process, a bony prominence behind the spinal cord, which shields the cord's nervous tissue from impact trauma. Vertebrae also have a strong bony "body" (vertebral body) in front of the spinal cord to provide a platform suitable for weight bearing of all tissues above the buttocks. The lumbar vertebrae stack immediately atop the sacrum bone that is situated in between the buttocks. On each side, the sacrum meets the iliac bone of the pelvis to form the sacroiliac joint of the buttocks.
The discs are pads that serve as "cushions" between the individual vertebral bodies. They help to minimize the impact of stress forces on the spinal column. Each disc is designed like a jelly donut with a central softer component (nucleus pulposus) and a surrounding outer ring (annulus fibrosus). The central portion of the disc is capable of rupturing
as described below.
Ligaments are strong fibrous soft tissues that firmly attach bones to bones. Ligaments attach each of the vertebrae to each other and surround each of the discs.
The nerves that provide sensation and stimulate the muscles of the low back as well as the lower extremities (the thighs, legs, feet, and toes) exit the lumbar spinal column through bony portals, each of which is called a "foramen."
Many muscle groups that are responsible for flexing, extending, and rotating the waist, as well as moving the lower extremities, attach to the lumbar spine through tendon insertions.
The aorta and blood vessels that transport blood to and from the lower extremities pass in front of the lumbar spine in the abdomen and pelvis. Surrounding these blood vessels are lymph nodes (lymph glands) and tissues of the involuntary nervous system that are important in maintaining bladder and bowel control.
The uterus and ovaries are important pelvic structures in front of the pelvic area of women. Theis a significant pelvic structure in men. The kidneys are on either side of the back of the lower abdomen, in front of the lumbar spine.
The skin over the lumbar area is supplied by nerves that come from nerve roots that exit from the lumbar spine.
What is the function of the low back?
The low back, or lumbar area, serves a number of important functions for the human body. These functions include structural support, movement, and protection of certain body tissues.
When we stand, the lower back is functioning to support the weight of the upper body. When we bend, extend, or rotate at the waist, the lower back is involved in the movement. Therefore, injury to the structures important for weight bearing, such as the bony spine, muscles, tendons, and ligaments, often can be detected when the body is standing erect or used in various movements.
Protecting the soft tissues of the nervous system and spinal cord as well as nearby organs of the pelvis and abdomen is a critical function the lumbar spine and its adjacent muscles.
What are common causes of lower back pain?
Common causes of low back pain (lumbar backache) include lumbar strain, nerve irritation, lumbar radiculopathy, bony encroachment, and conditions of the bone and joints. Each of these is reviewed below.
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 therapy, 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, ibuprofen, 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.
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 (lumbar radiculopathy), bony encroachment, and inflammation of the nerves caused by a viral infection (shingles).
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.
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.
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).
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.
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.
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.
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.
What is the treatment for low back pain?
So, how is low back pain treated?
Whether your low back pain is mild or severe, home treatment will be an important part of your care.
Acute low back pain
When you first feel back pain, try these steps to avoid or reduce pain:
Ongoing (chronic) low back pain -
- Relax. Find a comfortable position for rest. Some people are comfortable on the floor or a medium-firm bed with a small pillow under their head and another under their knees. Some people prefer to lie on their side with a pillow between their knees. Don't stay in one position for too long.
- Walk. Take a short walk (10 to 20 minutes) on a level surface (no slopes, hills, or stairs) every 2 to 3 hours. Walk only distances you can manage without pain, especially leg pain.
- Take pain medicine if needed, such as acetaminophen (Tylenol) or medicines that reduce pain, swelling, and irritation, including ibuprofen (such as Advil or Motrin) or naproxen (such as Aleve or Naprosyn). These medicines usually work best if you take them on a regular schedule instead of waiting until the pain is severe.
- Try heat or ice. Try using a heating pad on a low or medium setting for 15 to 20 minutes every 2 to 3 hours. Try a warm shower in place of one session with the heating pad. Or you can buy single-use heat wraps that last up to 8 hours. You can also try an ice pack for 10 to 15 minutes every 2 to 3 hours. You can use an ice pack or a bag of frozen vegetables wrapped in a thin towel. There is not strong evidence that either heat or ice will help, but you can try them to see if they help. You may also want to try switching between heat and cold.
To help relieve chronic low back pain, always try to:
- Exercise to help relieve back pain. See a therapist or other spine specialist for exercises specific to your condition. Studies show that doing exercises can help people with chronic low back pain return to their normal daily activities.
- Reduce the stress in your life.
- Get the support you need. Work with your doctor to come up with a chronic pain treatment plan. Ask family members of friends when you need help.
- Achieve and maintain a healthy weight.
- Try not to bend or twist your back as you lie down.
- Avoid smoking. Smoking slows tissue healing.
- Think through your daily activities and change those that may be causing back pain. Your list might include lifting a small child throughout the day, a long commute to work, sitting in front of a computer all day, wearing high-heeled shoes, or doing yard work or landscaping work.