What condition causes low back pain without radiation to the legs?

Nonspecific (Mechanical) Low Back Pain

Low back pain without radiation to the limbs is classified as nonspecific or mechanical low back pain, which arises intrinsically from the spine, intervertebral disks, or surrounding soft tissues and represents the most common presentation of low back pain. 1

Key Diagnostic Features

• Pain localized below the costal margin and above the inferior gluteal folds without extension below the knee distinguishes nonspecific low back pain from radiculopathy. 2

• Absence of dermatomal radiation is the defining characteristic—pain that does not follow a specific nerve-root distribution and does not extend down the leg below the knee. 3

• Negative straight-leg raise test (no reproduction of radicular pain between 30–70° of leg elevation) helps exclude lumbar radiculopathy as the cause. 3, 4

• No neurologic deficits on examination—normal motor strength, intact reflexes, and preserved sensation in the lower extremities differentiate this from nerve-root compression. 4

Clinical Course & Prognosis

• Patients without radiation fare significantly better than those with radicular symptoms—at 4 weeks, 28% are pain-free and 47% have diminished pain. 5

• The natural history is generally favorable, with most patients requiring minimal formal medical intervention. 6

Red-Flag Screening (Critical Step)

Even in the absence of leg radiation, systematically screen for serious underlying pathology:

• Progressive motor or sensory loss suggests evolving neurologic compromise. 1

• New urinary retention or overflow incontinence (90% sensitivity for cauda equina syndrome) mandates urgent MRI. 3, 1

• History of cancer increases the probability of malignant spinal disease from 0.7% to 9%. 3

• Fever, IV drug use, recent spinal procedure, or immunosuppression raises concern for spinal infection. 3, 1

• Significant trauma relative to age or chronic steroid use suggests possible vertebral compression fracture. 3, 1

Imaging Recommendations

• Do not routinely obtain imaging in patients with nonspecific low back pain during the first 4–6 weeks unless red-flag features are present. 7, 3

• Early imaging does not improve clinical outcomes and identifies many radiographic abnormalities that correlate poorly with symptoms but may lead to unnecessary interventions. 7

• Plain radiography may be considered for suspected vertebral compression fracture in higher-risk patients (osteoporosis, steroid use). 7

Management Algorithm

1. Confirm absence of radicular features: Pain does not extend below the knee, straight-leg raise is negative, and neurologic examination is normal. 3, 4

2. Systematically exclude red flags: Screen for urinary retention, cancer history, infection risk, progressive deficits, and fracture risk. 3, 1

3. If no red flags are present: Diagnose nonspecific mechanical low back pain and defer imaging for at least 4–6 weeks. 7, 3

4. Initiate conservative therapy: Prescribe NSAIDs, encourage continued activity (avoid prolonged bed rest), and consider physical therapy or yoga. 1, 8

5. Reassess at 4–6 weeks: If symptoms persist without improvement or new red flags emerge, consider plain radiography as an initial imaging option. 7

Common Pitfalls

• Mislabeling referred posterior thigh pain as sciatica—true radiculopathy requires pain extending below the knee in a dermatomal pattern. 3

• Overuse of imaging in the absence of red flags—routine MRI or CT does not improve outcomes and exposes patients to unnecessary radiation and potential false-positive findings. 7, 6

• Failing to screen for psychosocial barriers (fear-avoidance beliefs, work-related stress)—these factors predict chronicity and disability more than anatomic findings. 8