Common causes of back pain involve disease or injury to the muscles, bones, and/or nerves of the spine. Pain arising from abnormalities of organs within the abdomen, pelvis, or chest may also be felt in the back. This is called referred pain. Many intra-abdominal disorders, such as appendicitis, aneurysms, kidney diseases, bladder infections, pelvic infections, and ovarian disorders, among others, can cause pain referred to the back. Normal pregnancy can cause back pain in many ways, including stretching ligaments within the pelvis, irritating nerves, and straining the low back. Your doctor will have this in mind when evaluating your pain.
Nerve root syndromes are those that produce symptoms of nerve impingement (a nerve is directly irritated), often due to a herniation (or bulging) of the disc between the lower back bones. Sciatica is an example of nerve root impingement. Impingement pain tends to be sharp, affecting a specific area, and associated with numbness in the area of the leg that the affected nerve supplies.
Herniated discs are produced as the spinal discs degenerate or grow thinner. The jellylike central portion of the disc bulges out of the central cavity and pushes against a nerve root. Intervertebral discs begin to degenerate by the third decade of life. Herniated discs are found in one-third of adults older than 20 years of age. Only 3% of these, however, produce symptoms of nerve impingement.
Spondylosis occurs as intervertebral discs lose moisture and volume with age, which decreases the disc height. Even minor trauma under these circumstances can cause inflammation and nerve root impingement, which can produce classic sciatica without disc rupture.
Spinal disc degeneration coupled with disease in joints of the low back can lead to spinal-canal narrowing (spinal stenosis). These changes in the disc and the joints produce symptoms and can be seen on an X-ray. A person with spinal stenosis may have pain radiating down both lower extremities while standing for a long time or walking even short distances.
Cauda equina syndrome is a medical emergency whereby the spinal cord is directly compressed. Disc material expands into the spinal canal, which compresses the nerves. A person would experience pain, possible loss of sensation, and bowel or bladder dysfunction. This could include inability to control urination causing incontinence or the inability to begin urination.
Musculoskeletal pain syndromes that produce low back pain include myofascial pain syndromes and fibromyalgia.
Myofascial pain is characterized by pain and tenderness over localized areas (trigger points), loss of range of motion in the involved muscle groups, and pain radiating in a characteristic distribution but restricted to a peripheral nerve. Relief of pain is often reported when the involved muscle group is stretched.
Fibromyalgia results in widespread pain and tenderness throughout the body. Generalized stiffness, fatigue, and muscle aches are reported.
Other skeletal causes of low back pain include osteomyelitis (infections of the bones of the spine). Noninfectious inflammation of the spine (spondylitis) can cause stiffness and pain in the spine that is particularly worse in the morning.
Tumors, possibly cancerous, can be a source of skeletal pain. Inflammation of nerves from the spine can occur with infection of the nerves with the herpes zoster virus that causes shingles. This can occur in the thoracic area to cause upper back pain or in the lumbar area to cause low back pain.