Eighty percent of adult men and women in the United States have experienced low back pain, which can range from mild to incapacitating. The lumbar spine, or low back, consists of a complex network of interconnecting bones, joints, discs, nerves, tendons, nerves, ligaments, and muscles. Injury to any of these body parts can cause low back pain.
Doctors often categorize low back pain by how long it lasts:
- Acute low back pain usually comes on suddenly and may last up to a month.
- Subacute low back pain may last between four and 12 weeks.
- Chronic low back pain lasts more than 12 weeks.
Low back pain is often caused by the aging process. The discs in the low back tend to wear out, and joints and muscles can lose their ability to extend and contract as well as they used to. Osteoporosis, which is loss of bone density that can result from aging or certain illnesses, can also lead to low back pain.
Other culprits besides aging that may lead to low back pain are excess weight or pregnancy, both of which put stress on the back, as well as:
- Lifting, pushing, or pulling heavy objects or carrying objects for extended periods
- Hereditary and rheumatologic issues may predispose an individual to certain conditions (for example: ankylosing spondylitis, a form of arthritis that affects the spine)
- Incorrect posture, especially when lifting or carrying
- Sitting for long periods, particularly if an individual has poor posture or if there are poor ergonomics from improper computer screen height or lack of seatback support
- Smoking, which may inhibit vital nutrients from reaching the discs in the spine
- Standing for long periods, particularly with improper posture or footwear, because the muscles that hold the body upright can tire and a person may slump, causing the body weight to pull against ligaments in the lower back
- Stress that can lead to tense muscles in the back and cause pain
- Unaccustomed activity (think of the “weekend warrior”) or overuse, both of which can lead to strain or sprain
There are numerous spinal conditions that are associated with low back pain, including:
- Sciatica is a condition that can occur when a disc bulge compresses or irritates the sciatic nerve, which branches off the spinal cord at L4 to S3 (the fourth lumbar to third sacral vertebrae). The sciatic nerve is the largest and longest nerve in the body, extending from its roots in the spine to deliver and receive nerve signals all the way down to the feet. Thus, an aggravated sciatic nerve can affect parts of the body very far from the nerve root. For example, a compressed sciatic nerve can cause symptoms, like weakness, down to the foot. (Radiculopathy is a term doctors use to describe pain, numbness, or weakness that radiates from a nerve’s origin, and the symptoms a person feels relates to the parts of the body the irritated nerve serves.) The pain caused by sciatica is often described as a sudden shock or jolt or burning. When the sciatic nerve is compressed between a disc and the adjacent bone, an individual may also experience a “pins and needles” feeling, numbness, and/or weakness (like foot drop, a difficulty in raising the front of the foot) due to the nerve signal being interrupted. Sciatica can lead to numbness or loss of control in the bladder or bowel as well, for which an individual should seek immediate medical care.
- The sacroiliac joint, or SI joint, attaches the uppermost part of the hipbone, known as the ilium, to a large bone at the base of the spine, known as the sacrum, through ligaments. The sacrum consists of the vertebral segments S1 to S5. Inflammation in the sacroiliac joint, known as sacroiliitis, can lead to low back pain that can be felt on both sides of the back, down through the buttocks, hip, thigh, and back of the legs, and may be similar to the sciatic pain felt by a herniated disc. Symptoms may also include fever and stiffness.
- A herniated disc, slipped disc, bulging disc, or ruptured disc is a cause of back pain. It occurs when the round, jelly-like discs that act like shock absorbers between the spine’s vertebrae become compressed, bulge, or rupture. Most low back pain from herniated discs occurs in the lumbosacral region, often at L4-5 or L5-S1, which supports much of a person’s upper-body weight. (Vertebrae are identified with letters and numbers, starting with C1 in the neck, proceeding down through T in the thoracic vertebrae, L in the lumbar spine, and S at the sacroiliac joint.)
- Spinal stenosis in the lower back, also known as lumbar spinal stenosis, is the narrowing of the spinal canals, resulting in the compression of spinal nerve roots. It is often due to the degeneration of the joints and vertebrae in the spine.
Spinal stenosis can be worsened by the inflammatory disease osteoarthritis, which may hasten the breakdown of the cartilage in the facet joints. In addition, the ligaments of the spine may thicken in response, yet another factor leading to compressed spinal nerves.
Symptoms of lumbar spinal stenosis may develop gradually, reflecting the increasing compression of the nerve roots. The pain has been described as a “pins-and-needles” sensation, muscle weakness, and/or numbness. Sciatica, the radiating pain described earlier also known as radiculopathy, may be triggered as well.
- The decline of the vertebrae and joints in the spine, known as facet joints, is caused by the shrinking and drying out of the hydrated, cushiony discs. Nerve roots pass under the facet joints, which are made of cartilage and act like hinges to hold adjacent vertebrae together. The failure of the discs affects the facet joints because as the cartilage is worn away due to the lack of cushioning, the body replaces it with extra bone (known as a bone spur) – leading to compressed, aggravated nerves. This process of the degeneration of the joints and vertebrae is known as degenerative disc disease although it’s not really a disease but a condition that occurs, usually due to aging.
- Ankylosing spondylitis is a chronic inflammatory disease that causes inflammation between vertebrae and facet joints and between the spine and pelvis – rather than causing the degeneration seen in spondylosis. It may lead to the joints fusing together, resulting in pain and reduced flexibility. Other inflammatory diseases of the joints, such as osteoarthritis and rheumatoid arthritis, can also cause back pain.
- Spondylolisthesis is a condition in which one of the vertebrae in the spine slips out of the proper position and onto the vertebra below it. When spondylolisthesis occurs in children or teens, it is usually due to a birth defect or a traumatic injury. (In fact, spondylolisthesis is the most common cause of back pain in teens.) In adults, spondylolisthesis is usually caused by wear and tear in the spine due to aging and arthritis.
- Osteoporosis is a progressive decrease in bone density and strength that becomes more common with age. Osteoporosis may result in spinal compression fractures.
- A spinal schwannoma is a tumor that develops in the protective sheathing surrounding the nerve cells. Most spinal schwannomas are benign (not cancerous). However, even a benign tumor may need to be removed if it’s putting pressure on the nerves and spinal cord causing pain or other symptoms. If left untreated, schwannomas can grow, causing nerve and spinal damage.
- Osteomyelitis in the spine is a serious infection of the bone caused by bacteria or fungus and can affect children or adults. Symptoms can include severe back pain, neurologic symptoms, fever, swelling or warmth over the infected area.
- Curvature of the spine, such as occurs with scoliosis (a side-to-side curve, often S- or C-shaped) or loss of lordosis in the lumbar spine (the arch in the low back) may lead to low back pain because of pressure on the spinal discs, nerves, muscles, ligaments, or facet joints to compensate for the curve. Discitis refers to infection that occurs between the discs in the spine. Concentrated, severe pain is a symptom, and immediate medical attention is required.
- An abdominal aortic aneurysm is an enlargement in the low part of the aorta, the body’s major blood vessel, which extends from the heart and supplies blood to the rest of the body. Back pain can be a symptom indicating the aneurysm is growing and may rupture. Medical attention is required immediately.
- Fibromyalgia is a chronic pain syndrome. An individual with fibromyalgia may experience widespread muscle pain that includes low back pain.
- Kidney stones can cause severe pain in the low back that is usually on only one side, typically in the flank area.
- Cauda equina syndrome is a serious but rare neurological condition that is generally caused by the material in a ruptured disc being pushed into the spinal canal, causing compression of the cauda equina (the bundle of nerves in the lumbar canal that resembles a horse's tail). It causes loss of bladder and bowel control and is a medical emergency.
- Tumors are a rare cause of low back pain. Sometimes, they may originate in the back but usually they are a result of a cancer that has spread. A spinal tumor may be benign (noncancerous) or malignant (cancerous). It can develop within the spinal canal, the space in the vertebrae through which the spinal cord runs, or within the bones themselves.
- Endometriosis is the buildup of uterine tissue outside the uterus. It may cause low back and pelvic pain.