Low Back Pain Diagnosis – Simplified approach

Definition of Low Back Pain

Pain, muscle tension or stiffness localized below the costal margin and above the inferior gluteal folds, with or without leg pain.

Types of Low back pain:

  1. Acute (<6 weeks)
  2. Subacute (6-12 weeks)
  3. Chronic (>12 weeks)
  4. Recurrent: new episode after a symptom free period of 6 months and is not an exacerbation of chronic low back pain

Sciatica refers to the pain in the distribution of the lower lumbar spinal roots. The inflamed root generally presents as pain along radicular distribution while uninflamed compressed root generally presents as paraesthesia.

Although pain in the buttock might referred to that location from a lumbar spinal source, if buttock pain is the primary complaint it should be assessed in that context. It could indicate a local source of pain in the buttock muscles or indicate a hip problem.

Red Flag Signs in Low Back Pain

Red flag signs are the indicators of serious spinal pathology. Excluding red flag conditions in this manner does not guarantee that a red flag condition is absolutely not present. It establishes only that, for the present, further investigation is not warranted.

Mnemonic: TUNA FISH

Unexplained weight loss
Neurologic symptoms (Recent onset bowel/bladder dysfunction, Saddle anesthesia, progressive neurologic deficit in lower extremity, anal sphincter weakness)
Age >50 years
IV drug users
Steroid use
History of cancer (prostate, renal, breast, lung)

AllDuration of pain > 1 month
Bed rest with no relief
CancerAge ≥ 50 years
History of cancer
Unexplained weight loss
Neurologic findings
Compression fractureAge ≥ 50 years (> 70 years is more specific)
Significant trauma
History of osteoporosis
Corticosteroid use
Substance abuse
InfectionFever or chills
Recent skin or urinary tract infection or catherterization
Injection drug use
Fever (temperature > 100°F or 38°C)
Tenderness over spinous processes
Cauda equina syndromeSaddle anesthesia
Bilateral sciatica or leg weakness
Difficulty urinating
Fecal incontinence
Progressive motor or sensory deficit

Yellow Flag Signs in Low Back Pain

These are psychoscoial factors shown to be indicative of long term chronicity and disability.

  • A negative attitude that back pain is harmful or potentially severely disabling
  • Fear avoidance behavior and reduced activity levels
  • An expectation that passive, rather than active, treatment will be beneficial
  • A tendency to depression, low morale, and social withdrawl
  • Social or financial problems

Mnemonic: ABCDEF

Attitude: Negative
Behavior: Fair avoidance
Compensation issues
Expectation: Passive treatment better than active
Financial problems

Etiology of Low Back Pain

1. Non-specific/Simple Mechanical low back pain: Commonest cause

Mckenzie classification:

  • Postural syndrome: due to a mechanical deformation of normal soft tissue from prolonged end range loading of periarticular structures (static deformation of spine).
    • Pain may be local and reproducible when end range positions, such as slouching, are maintained for sustained periods of time.
    • Treated by improving posture and avoiding provocative posture
  • Dysfunction syndrome: due to adaptive shortening, scarring or adherence of connective tissue causing discomfort.
    • Consistent movement loss and pain at the end range of movement.
    • Treated by mobilization in the direction that reproduces pain (remodelling of tissues)
  • Derangement syndrome (commonest):
    • Due to disturbance in the normal resting position of the affected joint surfaces
    • May show one direction of repeated movement which decreases or centralizes referred symptoms – preferred direction.

Disc origin pain is aggravated by flexion and has a gradual onset while, the facet origin pain is aggravated by extension and has a more sudden onset.

2. Specific low back pain:

a. Mechanical:

  • Degenerative: Spondylosis, Intervertebral disc degeneration, Lumbar non-spondylolytic spondylolisthesis, Ankylosing spinal hyperostosis, Lumbar spina canal stenosis
  • Trauma: Lumbar intervertebral disc herniation, Vertebral fractures
  • Congenital: Spina bifida, Severe kyphosis, Severe scoliosis, Transitional vertebra

b. Non-mechanical:

  • Neoplasia: Multiple myeloma, Metastatic carcinoma, Spinal cord tumors, Lymphoma and leukemia, Retroperitoneal tumors, Primary vertebral tumors (Osteoid osteoma, Eosinophilic granuloma)
  • Inflammatoy arthritis: Ankylosing spondylitis, Reiter syndrome, Psoriatic spondylitis, Enteropathic spondyloarthritis (IBD)
  • Infection: Osteomyelitis (TB, Purulent), Paraspinous abscess, Septic diskitis
  • Osteochondrosis: Scheuermann disease

c. Referred: Renal, GI, Pelvic pathology or Aortic aneurysm

3. Psychogenic causes:

  • Anxiety
  • Depression
  • Fibromyalgia
  • Adjustment disorders at home, work, etc.

Inflammatory back pain: IPAIN mnemonic

1. Insidious onset
2. Pain at night
3. Age at onset <40 years
4. Improvement with exercise
5. No improvement with rest

ASAS classification for axial spondyloarthritis: SPINEACHE mnemonic

1. Sacroilitis on imaging (by radiograph or MRI) + >/= 1 of SPINEACHE OR
HLA-B27 + >/= 2 of SPINEACHE
a. Sausage digit (dactylitis)
b. Psoriasis-positive family history of SpA
c. Inflammatory back pain
d. NSAID good response
e. Enthesitis (heel)
f. Arthritis
g. Chron’s colitis/disease – elevated CRP
h. HLA-B27
i. Eye (Uveitis)

History Taking For Low Back Pain

1. Look for red flag signs in Acute Low Back pain and yellow flag signs in Chronic Low Back Pain

2. Where does it hurt?

  • Usually, dull steady ache over lower lumbar spine
  • Localized severe point tenderness in fractures

3. When does it hurt?

a. Disc related back pain:

  • Symptoms often worsened by sitting or standing for prolonged periods
  • Symptoms aggravated by coughing or sneezing
  • Symptoms often alleviated by lying flat

b. Lumbar spinal canal stenosis:

  • Symptoms improved by forward flexion of the back (opens up the narrowed spinal canal foraminal spaces) – “Shopping cart sign” (relief of pain when leaning forward to push shopping cart)
  • Symptoms worsened by standing or walking for prolonged periods and relieved by sitting (neurologic claudication)

c. Night pain: Malignancy, Infection, Ankylosing spondylitis

4. How does activity affect the pain?

  • Improved by rest, minimal on morning arising and worsened with activity: Mechanical back pain, Osteoarthritis
  • Improved by activity, worse on morning arisising and worsened with inactivity: Inflammatory spondyloarthropathy (ankylosing spondylitis, psoriatic arthritis or inflammatory bowel disease)
inflammatory vs mechanical back pain

A patient with back pain that is not aggravated by spinal movement warrants assessment for a cause of pain that refers pain to the spine. Abdominal aortic aneurysms can present in this way, and misrepresentation of the back pain.

5. Does the pain radiate?

  • Pain radiating down a leg may suggest nerve impingement:
    • One leg: Disc herniation
    • Both legs: Cauda equina syndrome, Cord compression
    • Disc herniation: Younger patients
    • Osteophyte: Older patients
  • Pain radiating to groin: Abdominal aortic aneurysm, Renal calculi
radicular pain vs referred pain

Pain in the buttock or proximal thigh is unlikely to be radicular pain but rather a somatic referred pain stemming from lumbar zygoapophyseal joints. Somatic pain can also be referred below the knee and even into the foot.

6. What relieves the pain?

  • Benefit noted or not with NSAIDs and acetaminophen: helpful in developing management strategy for pain control
  • Patients with a painful joint will feel better in postures that do not load that joint, e.g. lying down.
  • Pain not relieved by rest may indicate a serious pathology.

7. What are the associated features?

  1. Fever +/- History of recent surgical procedures or catheterization or skin infections: Osteomyelitis, Discitis, Epidural abscess
  2. Weight loss and history of cancer: Neoplasia or Tuberculosis
  3. Psoriatic skin lesions, Diarrhea: Seronegative spondyloarthropathy
  4. Vascular disease or cardiovascular risk factors: Aortic aneurysm
  5. Cough: Spinal metastases from lung cancer, Tuberculosis
  6. UTI or hematuria: Pain referred from genitourinary tract
  7. Urinary retention or poor stream: Prostatic carcinoma
  8. Menstrual period, AUB or abnormal menstruations: Gynecological cause
  9. Pain elsewhere: Systemic rheumatic diseases

8. What was the circumstance of onset?

  1. Spontaneous pain of an explosive onset: is alarming and may indicate spontaneous fracture or infection
  2. Twisting injury in flexed position: Tears of the anulus fibrosis, through tears of the zygapophysial joint capsules, to impaction and avulsion fractures of the articular processes, and fractures of the pars interarticularis
  3. Axial loading injury: Acute or fatigue failure of vertebral endplates, resulting ultimately in internal disc disruption

Pars interarticularis fracture commonly occur in sports people.

Physical Examination in Low Back Pain

low back pain examination
examination of back

1. Look – café-au-lait spots (? neurofibromatosis), hairy patches (? spina bifida), lordosis, list (abrupt planar shift of the spine, above a certain point, to one side), asymmetry, tight hamstrings resulting in an abnormal gait are considered to be a clinical feature of pars defects

List – deviation to opposite side: shoulder type PIVD
List – deviation to same side: axillary type PIVD

2. Feel – spinous process percussion tenderness (? fracture, tumor, infection), SI joint pain (? ankylosing spondylitis), chest expansion <2.5cm (? ankylosing spondylitis), step at L5 (? spondylolisthesis), paravertebral tenderness (tenderness anywhere from midline to midaxillary line)

Numbness or hyperesthesia over buttocks: entrapment neuropathies of superior cluneal nerves in patients with thoracolumbar pain

3. Move – pain on bending toward affected side, or on flexion (? Lumbar disc disease), pain on extension (? Facet joint or spinal stenosis), range of motion

4. Special Tests

a. Schober’s Test: assesses the amount of lumbar flexion. Make two pen-marks, one at 10cm above the PSIS, the other 5cm below it. Upon flexion, the distance should increase >5cm. Decreased ROM of lumbar spine suggests ankylosing spondylitis.

b. Straight Leg Raising Test (SLRT): assesses the presence of radiculopathy – if pain is reproduced and radiates down into affected leg when the leg is raised between 10 and 60 degrees elevation. If the opposite leg produces a positive response, it is indicative of a large herniation.

  • Lasegue’s test involves dorsiflexing the foot during the SLR.
  • Positive SLRT and Lasegue’s test indicates tension on nerve root L5 and S1.

c. Reverse SLRT or Femoral nerve stretch test: The reverse straight leg raise (RSLR) test or femoral tension sign detects tension in the L2–L4 nerve roots. With the patient prone, pain elicited in the anterior thigh with extension of the hip or flexion of the knee confirms a positive RSLR test.

d. Wadell’s sign indicating psychological distress (nonorganic causes of pain): 3 out of 5 is significant

Mnemonic: DOReST

  • Distraction testing: Inconsistent responses noted with the same test when performed in a standard fashion and when the patient’s attention is distracted (eg, seated straight leg raising without discomfort versus radiating pain with supine straight leg raise)
  • Overreaction: Inappropriate tenderness that is superficial or widespread
  • Regional disturbances: in strength and sensation that do not correspond with nerve root innervation patterns
  • Stimulation testing: Pain on simulated axial loading by pressing on the top of the head or simulated spine rotation
  • Tenderness: Localized tenderness that is does not follow a dermatomal or expected referral pattern; superficial light touch over the low back causing severe discomfort, or deep palpation causing widespread discomfort through the thoracic spine or sacrum or hips

5. Complete a thorough neurological exam, including gait, ankle reflex (S1), knee reflex (L4), strength, sensation (look for saddle anesthesia and anal sphincter tone, plus check dermatomes along lower limb).

Conditions such as radiculitis may cause both pain and neurological signs, but in that event the pain occurs in the lower limb, not in the back. If root inflammation also happens to involve the nerve root sleeve, back pain might also arise, but in that event the patient will have three problems each with a different mechanism: neurological signs due to conduction block, radicular pain due to nerve-root inflammation, and back pain due to inflammation of the dura.

low back pain neurological examination

Signs associated with specific nerve root impingement:

Nerve rootWeaknessAltered sensationAltered reflexe
L2Iliopsoas (Hip flexor)Anterior thigh, groinNone
L3Quadriceps (Knee extensor)Anterior and lateral thighPatellar
L4Tibialis anterior (ankle dorsiflexion; subtalar inversion)


AND Limitation of femoral stretch

Medial ankle and footPatellar
L5Extensor hallucis longus an Extensor digitorum longus (Great-toe dorsiflexion and other toe dorsiflexion) – Inability to heel walk


AND Limitation of SLRT

Lateral calf and 1st web spaceNone
S1Tendo-achilles, Flexor hallucis longus, Flexor digitorum longus (Ankle plantar flexion and plantar flexion of toes) – Inability to toe walk


AND Limitation of Bowstring/Sciatic nerve strect test (Perform SLRT; allow patient to flex knee back until pain is relieved; apply pressure to popliteal fossa; reproduction of pain indicates positive bowstring test)

Lateral plantar footAchilles
backpain syndromes

Examination of SI joint with tests like distraction test, FABER (PAtrick’s) test and Ganselen’s test is important.

There might be no abnormal findings in examination and in such cases referred pain to spine must be considered and visceral disorders must be sought for with abdominal examinations.

Hoover’s test/sign (for functional weakness): The patient is unable to extend the hip and to press the heel into the bed on request. The hip is extended involuntarily when the opposite leg is lifted off the bed.


low back pain investigations

a. X-rays: These are to be ordered in presence of red flag signs. ESR can be used as a screening test if malignancy and infection are concerned, which are very unlikely in patients with an ESR <20 mm/hr and no more than one risk factor for a systemic illness.

  1. Normal
  2. Abnormal but of no clinical significance: abnormalities not related to pain, such as spondylosis (disc narrowing – narrow discs tend more often to be painful; painful discs are not necessarily narrow, nor are all narrow discs necessarily painful), spina bifida occulta, transitional vertebrae, spondylolysis and spondylolisthesis
  3. Abnormal but of questionable clinical significance: abnormalities that may or may not be related to pain, and whose detection makes little or no difference to management, e.g. diffuse idiopathic skeletal hyperostosis
  4. Incidental or serendipitous abnormalities: conditions that may or may not be related to the patient’s pain, but which in their own right warrant treatment, e.g. Paget’s disease, osteoporosis
  5. Red flag conditions: osteomyelitis, discitis, paraspinal infections, tumours, fractures.

Pars blocks are the only means available by which to determine whether or not a radiographically evident defect is a symptomatic or an asymptomatic one.

6 Viewpoints 💬 on “Low Back Pain Diagnosis – Simplified approach”

  1. Thank you for this article, I am currently using it to study for my NP Finals. It is very thorough and comprehensive.

  2. Thank you for the great explanation!
    Could you tell us the source of each photograph you used from a book or site?
    Thank you in advace!

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