Back pain is a symptom. Pain arising from other organs may 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. 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 pinched), 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 in one spot and may be 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 most common between the ages of 30 and 40.
Spinal stenosis occurs as intervertebral discs lose moisture and volume with age, which decreases the disc spaces. Even minor trauma under these circumstances can cause inflammation and nerve root impingement, which can produce classic sciatica without disc rupture.
Spinal degeneration is caused by alterations in the disc that progress to degeneration. This, coupled with disease in joints of the low back, causes spinal canal narrowing. These changes in the disc and the joints produce symptoms and can be seen on an X-ray. A person with spinal degeneration may have morning stiffness or pain while standing for a long time or walking even short distances.
Cauda equina syndrome is a medical emergency. Disc material expands into the spinal canal, which compresses the nerves. A person typically experiences 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 pain and tenderness on 11 of 18 trigger points when touched, one of which is the low back area, as classified by the American College of Rheumatology. Generalized stiffness, fatigue, and muscle ache are reported.
Other skeletal causes of low back pain include osteomyelitis (infection of the bones of the spine) or sacroiliitis (inflammation of the sacroiliac joint). Tumors, possibly cancerous, can also be a source of skeletal pain.