Low Back Pain

Many people experience low back pain at some point in their lives, and most cases will resolve within days or weeks with minimal intervention. However, some patients experience recurrent episodes or persistent pain. A minority of patients have red flags indicating more serious etiologies. In this section, we review management of the following:

• General Low Back Pain

• Sciatica

General Low Back Pain

Low back pain can be nonspecific with a wide differential diagnosis including the following:

• compression fracture

• herniated nucleus pulposus

• paraspinal muscular strain/sprain/spasm

• spinal stenosis

• spondylosis (degenerative changes of the spine)

• spondylolisthesis (forward displacement of a vertebra)

• spondylolysis (defect or fracture of the pars interarticularis of the vertebral arch)

• connective tissue disease

• inflammatory spondyloarthropathy

• malignancy

• vertebral diskitis/osteomyelitis

• spinal epidural abscess

• referred pain from other conditions (e.g., pancreatitis, pyelonephritis, abdominal aortic aneurysm, nephrolithiasis)

Evaluation

The diagnosis can often be made based on history and physical examination alone (e.g., a positive straight-leg-raising test in patients with sciatica).

Red flags: Be aware of red flags that might indicate a more serious condition (e.g., cancer, cauda equina syndrome, fracture, infection), including:

• significant trauma (or minor trauma in older patients with osteoporosis)

• major or progressive motor or sensory deficit

• new-onset bowel or bladder incontinence or urine retention

• loss of anal sphincter tone

• saddle anesthesia

• history of cancer that can metastasize to bone (e.g., breast, lung, or prostate)

• pain increased or unrelieved by rest

• pain with unexplained weight loss

• prolonged history of glucocorticoid use

• intravenous drug use

• immunosuppression

• severe pain or history of spine surgery

• fevers

• recent infection (e.g., urinary, skin, bloodstream)

• osteoporosis

• pain lasting more than 4 to 6 weeks

Imaging: After a detailed history and physical examination, most patients without red flags do not require further workup with imaging or laboratory testing; these tests are often low yield and may lead to incidental findings that are unrelated to the cause of back pain and result in patient anxiety or unnecessary interventions.

However, when red flags lead to suspicion of a more serious condition, imaging should be pursued. The most appropriate choice and sequence of imaging studies (radiography, MRI, and/or CT) depend on the particular diagnoses that the clinician wishes to confirm or exclude.

• A radiograph is an appropriate first-line diagnostic imaging study when fracture or degenerative disease is suspected.

• MRI is the diagnostic imaging study of choice when infection, malignancy, or nerve or spinal cord compression is suspected.

• CT is indicated if an MRI is contraindicated (e.g., due to metallic implants).

• The American College of Physicians (ACP) best practice advice for diagnostic imaging of low back pain includes the following recommendations:

  • After a trial of therapy, imaging is indicated in certain patients who do not experience resolution of pain (e.g., ongoing radiculopathy or risk factors for inflammatory spine disease, compression fractures, spinal stenosis, and other conditions).

  • Imaging is also indicated when pain is worsening despite conservative therapy.

Laboratory tests: If infection or cancer is suspected, laboratory tests (e.g., erythrocyte sedimentation rate, C-reactive protein) should be obtained. Department of Veteran Affairs and Department of Defense issued a clinical practice guideline in 2022 for the diagnosis and treatment of low back pain that emphasizes the following:

• The history and physical should include evaluation for neurologic deficits and red flags.

• If present, diagnostic imaging and appropriate lab test should be obtained.

• If absent, the guideline strongly recommends against routine imaging studies or invasive diagnostic tests.

Treatment

Most patients can be treated with conservative measures in the ambulatory care setting. The ACP’s 2017 updated guidelines summarize the efficacy of various noninvasive pharmacologic and nonpharmacologic treatments of acute, subacute, and chronic low back pain. Unfortunately, the evidence to support any particular drug class or nonpharmacologic intervention is limited; thus, clinicians often must manage patients through trial and error, and obtain information about past treatments in patients who previously had episodes.

In the absence of red flags, initial treatment of acute or subacute low back pain should include the following steps:

• Counsel the patient to try conservative therapy for 4 to 6 weeks:

  • Provide advice to stay active, avoid bed rest, twisting, and bending.

  • Start a trial of nonpharmacologic treatment (e.g., heat, massage, acupuncture, yoga).

  • If pharmacologic treatment is desired, consider a short trial of a nonsteroidal anti-inflammatory drug (NSAID) if it is not contraindicated; acetaminophen is likely ineffective but reasonable to try as part of a multimodal approach.

  • Consider prescribing a muscle relaxant if pain is severe (although recent studies have not shown any benefit).

  • Consider referral for physical therapy (although studies are mixed on the efficacy of PT for the treatment of low back pain).

• Educate the patient:

  • Set reasonable expectations that most patients’ symptoms will improve in one month.

  • Provide educational resources (e.g., MedlinePlus).

• If pain persists after 4 to 6 weeks, consider the following:

  • switch to a different NSAID if not contraindicated

  • referral for PT

  • referral to a spine subspecialist

  • epidural, nerve-root or facet-joint glucocorticoid injections to hasten short-term pain relief (usually requires an MRI prior to treatment); these injections do not alter long-term outcomes

  • advanced imaging, especially in patient with worsening pain or pain that is refractory to conservative measures

• Components of treatment for chronic pain (typically lasting >12 weeks) include the following:

  • noninvasive nonpharmacologic treatments (e.g., exercise, multidisciplinary rehabilitation, acupuncture, cognitive behavioral therapy)

  • if response to nonpharmacologic treatments is inadequate, NSAIDs are first-line treatment, followed by duloxetine as a second-line therapy; however, many patients — especially older patients and those with comorbidities — have relative or absolute contraindications to NSAIDs

Pharmacotherapy: Gabapentinoid drugs (gabapentin and pregabalin) have been shown to be ineffective for low back pain. Opioids should only be considered if the above-mentioned therapies have failed and the potential benefits outweigh the risks. A 2018 randomized controlled trial compared the effect of opioid and nonopioid medication regimens in patients with chronic back, hip, and knee pain. Treatment with opioids was not superior to treatment with nonopioids for pain-related function, further supporting the recommendation to avoid opioids for chronic back and musculoskeletal pain.

Sciatica

Sciatica is characterized by pain that radiates from the low back or buttocks down the leg along the course of the sciatic nerve; its most common cause is a herniated disk. An estimated 5% to 10% of clinically evident lumbosacral disk herniations involve upper lumbar nerve roots (e.g., L2 or L3), which are in the femoral — not sciatic — nerve distribution; in these cases, radicular symptoms are generally limited to the thigh, whereas sciatica symptoms generally radiate into the lower legs. The following figure is a helpful review of the anatomy and causes of sciatica and shows that there are peripheral causes of sciatica, too.

(Source: Sciatica. N Engl J Med 2015.)

Diagnosis

Key features of sciatica (not present in all cases) include the following:

• aching, sharp pain, or both radiating from the low back or buttock and proceeding to the leg anterolaterally with L4 nerve root compression, dorsolaterally with L5 compression, and posteriorly with S1 compression (shown in the first figure below)

• typically, unilateral (but bilateral with central disk herniation, lumbar stenosis, and spondylolisthesis)

• not always accompanied by back pain

• exacerbation of pain with coughing, sneezing, or Valsalva maneuver (suggests disk rupture)

• numbness or paresthesia in dermatomal distribution

• muscle weakness in a minority of cases (e.g., weakness of great toe or ankle dorsiflexion with L5 involvement)

• diminished knee or ankle reflex (with L4 or S1 involvement, respectively)

• positive straight-leg-raising test result (good sensitivity, poor specificity) as indicated by reproduction or marked worsening of the patient’s initial pain and firm resistance to further elevation of the leg (see second figure below)

• positive crossed straight-leg-raising test result (good specificity, poor sensitivity) as indicated by sciatic pain in the opposite leg after raising the unaffected leg

Diagnostic Studies

Patients with clear evidence of sciatica without red flags often do not require imaging unless intervention is planned. When imaging is indicated, MRI without gadolinium can reveal the nature and location of disk rupture and spinal lesions. CT is performed less frequently but reveals most disk herniations and structural changes of the spine. In patients with a contraindication to MRI (e.g., some implanted pacemakers), a CT scan can be obtained. Needle electromyography (EMG) and nerve conduction studies can show the distribution of muscular denervation.

Treatment

Most patients with sciatica will improve without treatment (one-third within 2 weeks and three-quarters within 3 months). The following therapies are available for treatment of sciatica, but high-quality evidence of benefit is lacking.

• First-line treatment includes medication (NSAIDs) and PT. Even herniated disks can resolve with conservative management.

• Gabapentinoid (pregabalin) was not found to be effective in patients with sciatica in a well-done randomized trial. Initial pain from an acute herniated disk can be excruciating; hence, a brief course of opioid therapy may be unavoidable.

• Alternative therapies (e.g., spinal manipulation and electrical stimulation) have been shown to be beneficial in some lower-quality studies.

• Epidural glucocorticoid injections provide brief, short-term relief for some patients but do not change longer-term outcomes.

• Results from a randomized controlled trial demonstrated benefit from PT referral in patients with acute back pain from sciatica.

• Surgery is supported by some research because it provides early pain relief. However, a 2007 randomized trial did not find prolonged benefit of surgery at one-year follow-up. See NEJM Journal Watch for more on studies of surgery for degenerative lumbar spine disease and NEJM for a discussion of clinical decision-making around surgery.