Definition	Low back pain is pain, muscle tension, or stiffness localized below the costal margin and above the inferior gluteal folds, with or without leg pain (sciatica).1 It may be acute or chronic (persisting for 12 weeks or more).2 Nonspecific low back pain is low back pain not attributed to a recognizable pathology, such as infection, tumor, osteoporosis, rheumatoid arthritis, fracture, or inflammation.1 This review excludes low back pain or sciatica with symptoms or signs at presentation that suggest a specific underlying condition.
Incidence/Prevalence	More than 70 percent of people in developed countries will experience low back pain at some time in their lives.3 Each year, 15 to 45 percent of adults suffer low back pain, and one in 20 people present to a hospital with a new episode. Low back pain is most common between 35 and 55 years of age.3
Etiology/Risk Factors	Symptoms, pathology, and radiologic appearances are poorly correlated. Pain is nonspecific in about 85 percent of people. About 4 percent of people with low back pain in primary care have compression fractures and about 1 percent have a tumor. The prevalence of prolapsed intervertebral disc is about 1 to 3 percent.3 Ankylosing spondylitis and spinal infections are less common.4 Risk factors for the development of back pain include heavy physical work, frequent bending, twisting, lifting, and prolonged static postures. Psychosocial risk factors include anxiety, depression, and mental stress at work.3,5
Prognosis	Acute low back pain is usually self-limiting (90 percent of people recover within six weeks), although 2 to 7 percent develop chronic pain. One study found that recurrent pain accounted for 75 to 85 percent of absenteeism from work.6
Clinical Aims	To relieve pain; to improve function; to develop coping strategies for pain, with minimal adverse effects from treatment.2,7
Clinical Outcomes	Pain intensity (visual analog or numerical rating scale); overall improvement (self-reported or observed); back pain-specific functional status (such as Roland Morris questionnaire, Oswestry questionnaire); impact on employment (days of sick leave, number of people returned to work); medication use; intervention specific outcomes (such as coping and pain behavior for behavior treatment, strength and flexibility for exercise therapy, depression for antidepressants, and muscle spasm for muscle relaxants and electromyographic [EMG] biofeedback).