as sub-acute), or chronic. the specific duration required to meet each of these is not universally agreed upon, but generally pain lasting less than six weeks is classified as acute, pain lasting six to twelve weeks is sub-chronic, and more than twelve weeks is chronic. management and prognosis may change based on the duration of symptoms. red flags red flags are warning signs that may indicate a more serious problem red flag possible cause previous history of cancercancer unintentional weight loss loss of bladder or bowel controlcaudaequinasyndrome significant motor weaknessor sensory problems loss of sensation in thebuttocks (saddle anesthesia) significant trauma related to agefracture chronic corticosteroid use osteoporosis severe pain after lumbarsurgery in past yearinfection fever urinary tract infection immunosuppression intravenous drug use the presence of certain signs, termed red flags, indicate the need for further testing to look for more serious underlying problems, which may require immediate or specific treatment. the presence of a red flag does not mean that there is a significant problem. it is only suggestive, and most people with red flags have no serious underlying problem. if no red flags are present, performing diagnostic imaging or laboratory testing in the first four weeks after the start of the symptoms has not been shown to be useful. the usefulness of many red flags is poorly supported by evidence. the most useful for detecting a fracture are: older age, corticosteroid use, and significant trauma especially if it results in skin markings. the best determinant of the presence of cancer is a history of the same. with other causes ruled out, people with non-specific low back pain are typically treated symptomatically, without exact determination of the cause. efforts to uncover factors that might complicate the diagnosis, such as depression, substance abuse, or an agenda concerning insurance payments may be helpful. tests the straight leg raise test can detect pain originating from a herniated disc. when warranted, imaging such as mri can provide clear detail about disc related causes of back pain (l4–l5 disc herniation shown) imaging is indicated when there are red flags, ongoing neurological symptoms that do not resolve, or ongoing or worsening pain. in particular, early use of imaging (either mri or ct) is recommended for suspected cancer, infection, or cauda equina syndrome. mri is slightly better than ct for identifying disc disease; the two technologies are equally useful for diagnosing spinal stenosis. only a few physical diagnostic tests are helpful. the straight leg raise test is almost always positive in those with disc herniation, and lumbar provocative discography may be useful to identify a specific disc causing pain in those with chronic high levels of low back pain. therapeutic procedures such as nerve blocks can also be used to determine a specific source of pain. some evidence supports the use of facet joint injections, transforminal epidural injections and sacroiliac injections as diagnostic tests. most other physical tests, such as evaluating for scoliosis, muscle weakness or wasting, and impaired reflexes, are of little use. complaints of low back pain are one of the most common reasons people visit doctors. for pain that has lasted only a few weeks, the pain is likely to subside on its own. thus, if a person's medical history and physical examination do not suggest a specific disease as the cause, medical societies advise against imaging tests such as x-rays, ct scans, and mris. individuals may want such tests but, unless red flags are present, they are unnecessary health care. routine imaging increases costs, is associated with higher rates of surgery with no overall benefit, and the radiation used may be harmful to one's health. fewer than 1% of imaging tests identify the cause of the problem. imaging may also detect harmless abnormalities, encouraging people to request further unnecessary testing or to worry. even so, mri scans of the lumbar region increased by more than 300% among united states medicare beneficiaries from 1994 to 2006. prevention exercise appears to be useful for preventing low back pain. exercise is also probably effective in preventing recurrences in those with pain that has lasted more than six weeks. medium-firm mattresses are more beneficial for chronic pain than firm mattresses. there is little to no evidence that back belts are any more helpful in preventing low back pain than education about proper lifting techniques. there is no quality data that supports medium firm mattresses over firm mattresses. a few studies that have contradicted this notion have also failed to include sleep posture and mattress firmness. the most comfortable sleep surface may be preferred. shoe insoles do not help prevent low back pain. management most people with acute or subacute low back pain improve over time no matter the treatment. there is often improvement within the first month. recommendations include remaining active, avoiding activity that worsen the pain, and understanding self-care of the symptoms. management of low back pain depends on which of the three general categories is the cause: mechanical problems, non-mechanical problems, or referred pain. for acute pain that is causing only mild to moderate problems, the goals are to restore normal function, return the individual to work, and minimize pain. the condition is normally not serious, resolves without much being done, and recovery is helped by attempting to return to normal activities as soon as possible within the limits of pain. providing individuals with coping skills through reassurance of these facts is useful in speeding recovery. for those with sub-chronic or chronic low back pain, multidisciplinary treatment programs may help. initial management with non–medication based treatments is recommended non–medication based treatments include superficial heat, massage, acupuncture, or spinal manipulation. if these are not sufficiently effective, nsaids are recommended. acetaminophen and systemic steroids are not recommended as both medications are not effective at improving pain outcomes in acute or subacute low back pain. physical therapy stabilization exercises for lumbar spine and manual therapy have shown decrease in pain symptoms in patients. manual therapy and stabilization effects have similar effects on low back pain which overweighs the effects of general exercises. management of acute low back pain increasing general physical activity has been recommended, but no clear relationship to pain or disability or returning to work has been found when used for the treatment of an acute episode of pain. for acute pain, low- to moderate-quality evidence supports walking. aerobic exercises like progressive walking appears useful for subacute and acute low back pain, is strongly recommended for chronic low back pain, and is recommended after surgery. directional exercises, which try to limit low back pain, are recommended in sub-acute, chronic and radicular low back pain. these exercises only work if they are limiting low back pain. treatment according to mckenzie method is somewhat effective for recurrent acute low back pain, but its benefit in the short term does not appear significant. there is tentative evidence to support the use of heat therapy for acute and sub-chronic low back pain but little evidence for the use of either heat or cold therapy in chronic pain. weak evidence suggests that back belts might decrease the number of missed workdays, but there is nothing to suggest that they help with the pain. ultrasound and shock wave therapies do not appear effective and therefore are not recommended. lumbar traction lacks effectiveness as an intervention for radicular low back pain. it is also unclear whether lumbar supports are an effective treatment intervention. exercise programs that incorporate stretching only are not recommended for low back pain. generic or non-specific stretching has also been found to not help with acute low back pain. yoga and tai chi are not recommended in case of acute or subacute low back pain, but are recommended in case of chronic back pain. stretching, especially with limited range of motion, can impede future progression of treatment like limiting strength and limiting exercises. management of chronic low back pain exercise therapy is effective in decreasing pain and improving physical function, trunk muscle strength and the mental health for those with chronic low back pain. it also improves long-term function and appears to reduce recurrence rates for as long as six months after the completion of the program. the observed treatment effect for the exercise when compared to no treatment, usual care or placebo, improved pain (low‐certainty evidence), but improvements were small for functional limitations outcomes (moderate‐certainty evidence). there is no evidence that one particular type of exercise therapy is more effective than another, so the form of exercise used can be based on patient or practitioner preference, availability and cost. the alexander technique appears useful for chronic back pain, and there is some evidence to support small benefits from the use of yoga. if a person with chronic low back pain is motivated, it is recommended to use yoga and tai chi as a form of treatment, but this is not recommended to treat acute or subacute low back pain. motor control exercise, which involves guided movement and use of normal muscles during simple tasks which then builds to more complex tasks, improves pain and function up to 20 weeks, but there was little difference compared to manual therapy and other forms of exercise. motor control exercise accompanied by manual therapy also produces similar reductions in pain intensity when compared to general strength and condition exercise training, yet only the latter also improved muscle endurance and strength, whilst concurrently decreased self-reported disability. aquatic therapy is recommended as an option in those with other preexisting conditions like extreme obesity, degenerative joint disease, or other conditions that limit progressive walking. aquatic therapy is recommended for chronic and subacute low back pain in those with a preexisting condition. aquatic therapy is not recommended for people that have no preexisting condition that limits their progressive walking. there is low-to-moderate quality evidence that supports pilates in low back pain for the reduction of pain and disability, however there is no conclusive evidence that pilates is better than any other form of exercise for low back pain. patients with chronic low back pain receiving multidisciplinary biopsychosocial rehabilitation (mbr) programs are likely to experience less pain and disability than those receiving usual care or a physical treatment. mbr also has a positive influence on work status of the patient compared to physical treatment. effects are of a modest magnitude and should be balanced against the time and resource requirements of mbr programs. peripheral nerve stimulation, a minimally-invasive procedure, may be useful in cases of chronic low back pain that do not respond to other measures, although the evidence supporting it is not conclusive, and it is not effective for pain that radiates into the leg. evidence for the use of shoe insoles as a treatment is inconclusive. transcutaneous electrical nerve stimulation (tens) has not been found to be effective in chronic low back pain. there has been little research that supports the use of lumbar extension machines and thus they are not recommended. medications the management of low back pain often includes medications for the duration that they are beneficial. with the first episode of low back pain the hope is a complete cure; however, if the problem becomes chronic, the goals may change to pain management and the recovery of as much function as possible. as pain medications are only somewhat effective, expectations regarding their benefit may differ from reality, and this can lead to decreased satisfaction. the medication typically recommended first are acetaminophen (paracetamol), nsaids (though not aspirin), or skeletal muscle relaxants and these are enough for most people. benefits with nsaids is thought to be small. acetaminophen (paracetamol) may be no more effective than placebo at improving pain, quality of life, or function nsaids are more effective for acute episodes than acetaminophen and may be slightly more effective that placebo; however, they carry a greater risk of side effects, including kidney failure, stomach ulcers and possibly heart problems. thus, nsaids are a second choice to acetaminophen, recommended only when the pain is not handled by the latter. nsaids are available in several different classes; there is no evidence to support the use of cox-2 inhibitors over any other class of nsaids with respect to benefits. with respect to safety naproxen may be best. muscle relaxants may be beneficial. systemic corticosteriods are sometimes suggested for low back pain and may have a