Low Back Pain

This topic deals primarily with Low Back Pain, around the waist, certainly below the belly button. Most of it could also apply to upper back pain, but some of the conditions (esp. herniated disk) are much less common there.

The vast majority of cases of Low Back Pain are due to 3-4 conditions, diagnosed primarily by a physical exam. Pain from most of the conditions discussed below might or might not come and go, but the ones with asterisks (*) will persist until they resolve on their own, or worse.

Causes of Low Back Pain

Main Causes to ConsiderUncommon Conditions Not to Forget
Muscle Strain or Spasm / Ligament Sprain
Herniated Disk (includes Sciatica)
Spinal Stenosis
(simply due to age)
Bone Disease *

Spinal Cord Disease *
Bone Cancer
(esp. if elderly) *
Ankylosing Spondylitis
Abdominal Diseases *
Herpes Zoster (Shingles) *

Most back pain is due to non-serious Strains, Spasms, and Sprains, that almost always get better on their own eventually.ย  We diagnosis these after ruling out other conditions. But first, we’re sure to exclude some unusual causes which can be catastrophic.

Acute New-Onset:  Consider Rare but Serious Causes

  • Drug Injector with fever:ย ย maybe Spinal Cord Disease: Epidural Abscess ย โ†’ Send to ER for MRI !
  • History of cancer (breast, prostate, lung):ย  maybe Spinal Cord Disease: Epidural Metastasis ย โ†’ Send to ER for MRI !!!
  • Tingling around genitals and anus, major incontinence (urine or stool) or inability to pee all day (with abnormal anal reflex & leg weakness on exam): maybe Spinal Cord Disease: Epidural Abscess / Metastasis ย โ†’ Send to ER for MRI !!!
  • Weakness in both legs: may be Spinal Cord Disease ย โ†’ Send to ER for MRI !!! (Must be true loss of strength on physical exam, tested by lifting the leg against resistance. If able to walk on heels, likely no weakness)
  • Pain does NOT GET WORSE with bending or movements, or palpating the back: maybe Abdominal Disease (kidneys, ectopic pregnancy, aortic aneurysm) [see topic Abdominal Pain]
  • Fever:ย  maybe Epidural Abscess or Bone Infection or Abdominal Disease [see Full Text]ย  (note: fever with pain all over entire back is probably the Flu, or Covid)
  • Elderly: maybe Bone Cancer, needs an X-Ray [see below for exam]

Most Cases of Low Back Pain

The vast majority of cases are due to non-serious Sprains, Strains, or Spasms, that almost always get better on their own eventually.ย  We diagnosis these after ruling out other conditions:


  • Pain or tingling that goes down just part of the leg, to the foot, suggests Herniated Disk (includes Sciatica)
  • Pain with walking, that eases after a few min. of sitting or lying, OR if walking feels better while bent over (like leaning on a shopping cart) suggests Spinal Stenosis (usually the elderly)
  • Pain that’s worst early morning on arising (lasts at least 30-60 min.), then eases up, may be Ankylosing Spondylitis.  Age <40.  (Order tests Sed Rate (ESR) or CRP; and a Sacroiliac joint x-ray)

Physical Exam (what we as examiners seek):

1.  Ranges of Motion: Patient bends forward, back, to sides, twists, to evaluate level of disability

2.  Tap firmly on each bone in the spine (vertebrae)

  • Only one hurts:  X-Ray to rule-out Bone Disease (including cancer)
  • Only one hurts AND ALSO a suggestion of Epidural Disease (Abscess or Metastasis, see above): to ER for MRI
  • Lots of vertebrae hurt:  Unlikely to be anything serious (non-specific finding that doesn’t point anywhere)

3.  Palpate (press on) the muscles to either side of the spine

4.  Test Muscle Strength Against Resistance in the Legs

  • Weakness in 1-2 joints of 1 leg, in patient with tingling down leg to foot in distribution of a nerve, suggests Herniated Disk.ย  Most important joint to test is the Big Toe!
  • Weakness in both legs suggests Spinal Stenosis (esp. if elderly) or rare Spinal Cord Disease (if risks & other symptoms, see above)
    • Ability to walk on heels, and on tiptoes, strongly suggests there’s no true muscle weakness

5.  Test Leg Reflexes (esp. the Heel, also the Knee)

  • Decreased reflex on 1 side (esp. the heel) suggests Herniated Disk
  • Absent reflexes on both sides suggests Spinal Stenosis (or a rare Epidural Disease if other findings suggestive) (or, more commonly, inability of examiner to get the reflex)
  • Truly “hyperactive reflexes,” as noted by a trained examiner, suggests serious epidural or spinal cord disease

6.ย  Straight-Leg Raise Test (see Full Text)ย  —ย  suggests Herniated Disk if positive

7.  Rash running on just one side of back & down part of one leg  =  Herpes Zoster (Shingles)

Who Needs an X-Ray

  • Tenderness when we tap firmly on only one vertebra (for Bone Cancer)
  • Elderly with new low back pain (for metastatic Bone Cancer)
  • Possible Ankylosing Spondylitis (Sacroiliac Joint x-ray; see Full Text)
  • Chronic low back pain: one-time x-ray may diagnose Osteoarthritis if elderly, or undetected Scoliosis from childhood
  • NOTE: Since x-rays only show bone diseases, & most low back pain isn’t caused by them, x-rays are rarely useful

Who Needs an MRI

  1. Possible Spinal Cord Disease (send to ER)
  2. Probable Herniated Disk by history & physical exam, with pain that’s lasted 3-4 months, AND patient desires surgery (esp. if there’s also muscle weakness in a leg)
  3. Probable Spinal Stenosis on history & physical exam, especially if muscle weakness in the legs, AND patient desires surgery
  4. NOTE:ย  Since studies show many people without any pain have MRI abnormalities that look like Herniated Disks or Spinal Stenosis, the test is useless unless we have good clinical reason to suspect the disease, by history / exam
  5. NOTE:ย  Since most Herniated Disks and also Spinal Stenosis get better on their own in 3-4 mos., and the only other treatment we have is surgery, there’s no point in doing an expensive MRI if a patient has no interest in operations.

See Low Back Pain โ€” Full Text for more in-depth explanations and discussions.

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